Aeronautics Nationaladvisorycommittee

AERONAUTICS

NINTH ANNUAL REPORT

OF THE NATIONALADVISORYCOMMITTEE FOR AERONAUTICS

1923

INCLUDING TECHNICAL REPORTS hTos. 159 TO 185

WASH.IXGTOX GOVERNMENTPRINTINGOFFICE 1924 Particular attention is invited to the four portions of this report summarized below: The report on the fundamental principles of the Air MaiI Service submitted to the late President Harding at his request—Development of night flying and the establishment of regular transcontinental mail service is urgeci. (See page 11.) The statement of the need of Eederal legislation for the regulation and licensing of aircraft, airdromes, and aviators, and for the encouragement of the development of commercial aviation generally. (See page 14.) The explanation of the reIation of aeronautical research to nationaI defense—No limitation on the use of aircraft in warfare-lmmy and Navy defense programs influenced by the rapid development of the art of aviation-Aviation progress dependent upon scientific research— In this respect at Ieast America is pro~iding well against unpreparedness. (See page 54.) The conclusion of the report, summarizing Amer- ican achievements of pojxdar interest during the past year—What is holding back corrm~er- cial aviation-ATecessity of greater appropriations to maintain adequate air services in Army and Navy. (See page 55.)

— LETTER (M? SUBMITTAL.

To mix CONGRESSOF TEE UNITED STATES; ln compliance with the prm-isions of the act of Mkreh 3, 1915, establishing the Natiord Advisory Committee for Aeronautics, 1 submit herewith the ninth mmuaI report of the committee, for the fiscal year ended June 30, 1923. The attention of & Congress is invited to Lhe conclusion of the committee’s report, -which cont~ins constructive recommendations for the advancement of aeronautics, civil and military. I wish especially to indorse the recommendation of the Natio~d Advisory Committee for Aeronautics for the establishment of a Bureau of Civi Aeronautics in the Department of Com- merce. 1 concur in the committee’s views as to the necessity of scientific research and the importance of proticibg for continued development of military and mL~al aviation if America is to keep abreast of other nations. CALT-LXCOOmGE. THE WBITE HOUSE, December 10, 1923= 111

LETTER OF TRANSMITTAL.

NATIONAL ADVISORY COMMITTEEFOR AERON-AUTICS? Tdtington, D. C., .iYarember 231 i&?3. J&r. PRESIDENT: In compliance with the protiions of the act of Congress approved March 3, 1915 {Public ATO.273, 63d Cong.), 1 have the honor LO transmit here-with the ninth mnuaI report of the National Advisory Committee for Aeronautics, incIuding a statement of expenditures for the fiscal year ended June 30, 1923. During the past year there has been remarkable progress in aeron~ut ical demloprnent. .4 speed of 4+ miles per minute has been attained and ne~ records made for airplane endurance md economy of operation. The ak maiI sertice, by flyirg through the night on schedule, has demonstrated that, as soon as authorized, a reawhw transcontinental mail service within 36 . hours can be given the American people. The cumukti~e evidence of aeronautical progress since the wrnistke would} if fulIy appreciated} stir the imagination of far-seeing people} especially .imerican business men, for air navigation as an improved means of transportation is destined to become as re-rolutionary and as indispensable as the automobile. The airplane, however, is also becoming a more =iitd implement of -mar. Ayiation will be the first branch of either the Army or the A’avy to come into action in the future, and supremacy in the air will be practicality essential for uItimate success. With this in mind: zmd recoa@zing the need for retrenchment in governmental expenditures generalIy, it is the jud=gment of the National Ad-risory Committee for Aeronautics thzt it is unwise economy to withhold from the air services of the Army and the L’a-ry the funcls necessary for their de-re~opment and for their adequate equipment and maintenance. RespectfuMy submitted. hTATIOXU AMISORY COMMITTEEFOR .4EROXAUTICS, CHARLES D. WALcOT~, Chairman. The PRESIDENT, The Wkde House, Tashingion, D. C. .,.

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Letter of subtittiti ------Letter of tmmtittal------Ntith-ual reprt ------Fmctions of thecotittee ------Organization oftieeodttee ------31@@sof theqtkcotittee.. ..---- .---- .---- .------.----- .------. . ------~e=wutive cotittee ------—. Subc&ttees ------Qtiersfor cotittee ------The Lmgley Nemo&I Aeronautical Labomto~------Oticeof AerowuticaI In@lHgence ------Ctidemtian ofaerwutical ti~entiom ------Useofnon-go~ernmental agencies.. . . ------(~mpemtion oftiymd Na~y ------Investi~tiom undertaken forthehmy mdthe Na~------SpeciaI Committee on Desigmof Naq R~ldfistip ZR-l ------Special Cdtteeon Des~nof&my Se*d&fip RS-l ------American aerorrautical safety code-. ------Intermtimi s@ndw~zation of*dtunelrwtiti. ------Fundamentd purposes of the Air Uail Sertice ------Theneed of Federal legislation--- . ------Canada’s continued cmmtesytoAmericanairpi lots. ------Intentional &r Con~------Repofiof Cdtteeon Aertiy-cs ------Fteport o[Committee on Power Plants for&rcmft. -.---- ..------L ------Reptiof Cotittee on Materials for&croft ------Tectical pubbcations of thectittee ------Bibfi~phy of aeronautics ------Ftiancial repti ------Eetimawtioml &wt ------Rek+tion hetween aeronautic research and ticmftd&gn ------Advantages of the Amwicans @.emforae ronauticalresemch. . ------Rektion ofaeronauticaI rwmchto mtiomIdefemw ------Conclmion ------Ap~ndix ...... ------...... m TECHNICAL REPORTS. P&gc No. 159. “.Iet. J?ropukionfor Air-planes, ” bf- Edgar BLlckillgl]a~n... --.. __---- _-. _.. __-. ---_.. _---= z? No. 160. ‘(An Xlrship Slide R~lle,” ‘oy E.R. Weaver and S. F. Pickering ------91 NO. 161. ‘(The Distribution of Lift Over WingTipsarrd Ailerons,’: by David L. Bacon ------103 NO. 162. “CornpleteStudyof Longitudinal Oscillation ofa VE-7.4irpIa.ue, ”by F. H. Xortorr and 1}’. G. Brolvll.-_-______-_-p ______. ------.-._-__-_.-_.-_.------.:- 127 Xo. 163. “TheVertical, Longituriiual, and Lateral .Icceleratiorrs Experienced by rrn S. E, 5A .lirpIane l\~hiie LIane~~verii]g,’’ byF. H. NortonandT. Carroll ------133 $/0.164. “TJreInertiaC oeffieientso fan Airdlipi naFrictionles sFhlid, “byH. Bat@mall ------139 J~O. 165. “Dial)llragmsf or. Lero~]a[Itie Instruments, ” by M. D. Hersey ------155 NO. 166. “TheAerodynzrmic Plane Table, ” by.+, F. Zah]n ------._._=-__---.__._-- 1s7 L~O. 167. “TheMeasuremeut of theDa.mpingin Roll ona JN4hin Flight, ” by F. H. Norton- ..--== 199 Yo. 16S. “The General Efficiency Currc for Air PropeUers, ” by WaIterS. Diel~l ------205 No. 169. “The Etfectof AirfoiI Thickness and Plan Forrnon Lateral Control, ” by H. I. Hoot. ------217 No. 170. ‘[.l Studyof Longitudinal Dynamic Stabilifyi nl?light, ” by F.H. Norton ------Z2Q No, 171. '' Engille Perforlllallce ancitlle Deterlni]lation of Al>sd{]te Ceding, ''by Walter S. DichI. .. ---- 239 No. 172. ``Dyllarnie Stal]ility as Mectedby tile Lo]~gitli(liI~al Momenfof Inertia,’) by Ertwin B. H’ilson- 251 ● No. 173. ``Reiiable Forml)lae for Estin)ating .lir~)la]]e Perforluar~cc andtl~e Effects of Cl~angcs i[~lYeigtlt, Wing Aera, or Power,” by WalterS. DiehI ------359 No. 174. “TheSmaIIA rrguIar OscilIationsof Airplane sinStead yFlighf,’’byF. H. Nortuu ...... --_. _ 2s1 No. 175. “Arra.Jysis of W. F. Durand’s and E. P. Ledey’s Pro@er Tests, ” by Max Jf. 311mk ------2s’3 lNO. 17G. “A Constant Pressure Bomb, ” by F. W. Stevens ------303 No. 177. ‘(The Effect of Slipstream Obstructionson Air Propellers,” byll P. Lesleyanri B. AI. \J’wdti-- 311 lNo. 178. “RclativeE tJiciency of Direct and Geared Drive Propellers, ” by Walter S. Dichl ------335 Ilo. 179. ‘{The Effect of Elmtrodc Tenlpcratur eontheSparkirr gVoltageof Short Sprirk (ltips;’by F. B. =,- * SiIsbee------.-_------____---__-__----___.-__::_--"~______-_-_.-----_-.---~-.-_-__- No.180. “Deflectionof Beal~~s ~-itl~Specia.lR efere]lcet oShearD eformatio]~s,'' byJ..k.XclvliI]al]dCr.li”. Traj-er ------. ..-..-._.--.-__-.-.-s___ -.._. .__--_. ..--.. ..------— 3% NO. 181. “Form Factors of Beams Subjected to Transverse Loading OiLly,” by J. .L A’ewlin and C,. l\”, —.—. — -— Tracer _-.-. ___.-.. <------.----—------—— ------._--_.-----s.-_--_------s 375 No. 182, ‘(AermfynamicC haracterisficsof Airfoils-III, ” by ~~atiorral Advisory Corumiitce for .$ero- na~[tics--..---_-=------.._-----__~--__..---=------_--_-.-:--__-.--.~C: 3%5 NO. 183. '( The Arlalysis of Free Flight Propeller Tests aud Its Ap])lication foDcsign, ''by Max M. Jlunk- 439 No. 184. “TheAerocIynamic Forces on Airship Hulls,” by MaxYI. ~lllnk ------== 451 ~0, 185. ‘(The ResistanccfIf Sphercsirr Wind Tunnclsarrclin Air, ” byD. L. Bacon an(] E. G. Rcirl.... 4G9 I“rlr NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.

3341X.AW BUILDING,WA.SHHGTOX,D. C.

[“CHARLESD. ~.4LCOTT, SC. D., ~kzirman, Swretaw, ~~~.ofin Imtiiution, N%ehington, D. (~. D.AWDIV.TAYLOR,D. Eng.,Serretmy, Waehin.gton,D. t?. ,~OSEPHS. .&xEs,Ph. D., Chairman, ~mcutire ~O~rnitke, Director, Phys&J Laboratory, Johm. Hopkins lrni~ersit y, Baltiniore, Md. (“;EORGE K. BURGESS, Sc. D., Director, Bursau of Standards, Washington, D. C. WILLIAM F. DURAND, Ph.D., Prof~or of MechaticaI Engineering, Stanford ~~ni~-ersity, CaIifornix. .TEROKE(2. HUXSAKER2 Commander, United States Xavy, Bureau of .+eronautica, Navy Department, _Kas!nir@m, D. C. ~“~ARLES F. ~LARUX, ]i. E., (%ief, United States ‘We~ther Bnreau, Washin@m, D. CT. IA WREXCE W. MCINTOSH, Major, United States .bmy, Chief, Enetieering Dirision, Air Sem-ice, Dz@on, ohio. WILLLXUA. 310FFETT,Rear Admiral, l_’nited States ?ia.vy. ~Mef. B urean of Aeronautics, N-aT-j-D epmtrnent, Washington, D. ~. 3[ASON31.F’AmICK,31ajor GemeraI, United States Army, Chief of .ti Ser-rice, War Department, Washington, D. C. S. ~. STRATTOX,%. D., President, Massachusetts Institute of TecbnoIogy, Cambridge, Mass (jRYfiLEWRIGHT,B. S., Dayton,OhiQ EXEIWTNE (X)MMTTEE. JOSEPHS. AMES,Chairman. DATIDK. TAYLOR,Semetmy. {;F,ORGEK. BLTRGESS, MASONM. PATRICK, .JEROXEC. HUNSAKER, s. w. STRATTOX, bARLES F. ~~R~IX, CHARLES D. W=wr-r, LA KREXCE TV. MCIXTOSE, ORmLE WRIGHT. > W’mLrA>l .k. MOFFETT, NINTH ANNUAL REPORT OF THE NATIONALADVISORYCOMMITTEEFOR AERONAUTICS.

~AsmmToY, ~. C., ~’owmb 14, 1923. To the Congress: III accordance -with the provisiori of the act of Conggess approved March 3, 1915, establish- i~~ the &Tational Advisory Committee for Aeronautics, the committee submits herewith its ninth annual report. In this report the committee. has described its activities during the pask -year, the technical progress in the study of scienti6c prob~ems relat~~ to aero~au’t~csl the as~~tance rendered b-y the committee in the fmmmlation of policies for the general de-relop- rneut of aviation, the regdation of air navigation, the coordination of research work in general, the examination of aeronautical inventions, and the collection} analysis, and distribution of scientfic and technical data. This report also contains a statement of expenditures and recom- . mendations for advancing the science and art of aeronautics.

FUN(?TION3 O?FTHE COIIL%WFTEE.

The National Advisory Cmnmittee for Aeronautics -was established by act of Congress appro~ed March 3, 1915. The organic act charges the committee with the supervision and direction of the scientific study of the problems of ilighk mith a vie-w to their practical solution, the determination of problems which should be experimentally attacked, their instigation and application to practical questions of wronaut.ics. The act also authorizes the committee to direct and conduct r~earch and experimentation in aeronautics in such laboratory or laboratories, in whole or in part, as may be placed under its direction. Supplementing the prescribed dut& of the committee, its broad general functions ma-y be stated as foIlovrs: First. Vnder the law the committee holds itself at the service of any department or agency of the Go~ermaent interested in aeronautics> for the furn_k&mg of information or assistance in regard to scientific or technical matters relating to aeronautics, and in particular for the investigation and study of problems in this field with a view to their practical solution. Second. The committee may also exercise its functions for any indkidual, firm, association,’ or corporation within the _United States, provided that such individual, firm, association, m corporation defray the actmd cost in-roIved. Third. The committee institutes research, investigation, and study of problems which, in the judgment of its members or of the members of its -rarious subcommittees, are needful and time~y for the advance of the science and art of aeronautics in its wrious bmnches. Fourth. The committee keeps itself advised of the progress made in research and experimental work in aeronautics in all parts of the world, particulmly in England, France, Italy, Germany, Austria, and Canada. Fifth. The information thus gathered is brought to the attention of the various subcommit tees for consideration in connection with the preparation of programs for research and experimental work in this country. This information is also made a-railable promptly to the military and naval air services and other branches of the (iovermnent, and such as is not confidential is immediately released to Uni-rersity laboratories and aircraf~ manufacturers interested in the study of speci.fw problems, and aIso to the public.. Skth. The committee holds itself at the service of the President, the COngreSSf and the executive departments of the Government for the consideration of special problems which may be referred to it. 1 ~ REPCIRTXATIOA’ML ADVISORY COMMITTEE FOR AERONAUTICS.

ORGANIZATION OF THE COMMITTEE.

The committee has 12 members, appointed by the President. The law prm-ides that the personnel of the committee shalI consist of two members from the War Department, from the office in charge of military aeronautics; two members from the N’avy Department, from the office in charge of naval aeronautics; a representative each of the Smithsonian Institution, the United States Weather Bureau, and the United States Bureau of Standards; and not more than five additional persons acquainted with the needs of aeronautical science, either civil or miIitary, or skilled in aeronautical engineering or its allied sciences. Ml members as such serve without compensation. During the past year Maj. Lawrence TV. Mclltosh, United States Arlny, was appointed by the President a member of the committee to succeed Maj. Thurman H. Bane, United Sttites Army, who retired from ac~ive duty in the Army. The President has also appointed to mcmher- ship on the committee Dr. George K. Burgess~ who s-ucceeded Dr. S. W. Stratton as Director of the Bureau of Standards. Dr. John F. Hayford, of hTorthwestern University, Evanston, Ill., resigned, and the vacancy thus caused, was fiIled by the President by the reappointment of Doctor Strat Lon from private life, because of his keen interest, as president of the Massa- r,hnsetts institute of Technology, in the fundamental problems of aeronautics. The entire committee meets twice a year, the m_nuaI meeting being held in October and the semiannual meeting in ApriI. The present report incIudes the activities of the committee . between the annual meeting held on October 19, 1922, and tha~ heId on Octuber 18, 1923. The organization of the committee at the close of the past year was as foIlows: Charles D. Walcott, Sc. D., chairman. S. IV. Stratton, SC- D., secretary. Joseph S. Ames, Ph. D. George K. Btirgess, Sc. D. William F. Durand, Ph. D: Commander Jerome C. Hunsaker, United Staies N’avy. CharIes 1?. Marvin, M. E. Maj. Lawrence MT.~fcIntosh, United States bmy. Rear Admiral ‘WilIiam A. Moffett, United Stat,e.s Navy Maj. Gem Mason M. Patrick, United States Army. David W. Taylor, D. IZng. Or-riHe Ti’right, B. S.

MEETINGS OF THE ENTIRE COMMITTEE.

The semiannual meeting of the entire committee -was hekl in Wwhington on April 19, ~923, and the annual meeting on October 18, 1923. At these meeti~~s the committee reviewed the general progress in aeronautical research and discussed the problems that should be a~twked. Administrati~e reports were submitted by the secretary and by the Director of the Oflce of Aeronautical Intelligence. At the semiannual meeting Doctor Taylor made a report on the research work in progress uncler the committee’s direction at the Langley Nemorial Aeronautical Labomtory at LangIcy Field, Vs., and exhibited and explained relief models showing the distribution of pressure o-w the surfaces of an airpIane in actual flight.. .4t the annual meeting Doctor Ames, chairman of the executive committee, made a cGJn- plete report of the research work in progress at Langley l?iekl, in the course of which he exhibited lantern slides showing the methods used and the results obtained, Doctor Ames FJSOreported on the general progress End needs of the committee’s laboratory at LangIc.y Field. CM13cersof the committee were elected for the ensuing year, as folio-ws: Dr. Charles D. Walcott, chairman; Dr. David W. Taylor, secret my; Dr. Joseph S. Ames} chriirmfin executire committee. REPORT A;ATION”.L A-D$’ISOP>YCOMMITTEE FOR AEROA7A.UTICS. 3

TKE EXECUTIVECOMMITTEE.

For cimqying out the work of the Advisor! Committee the regulations protide for the election annuaIIy of m executi~e committee$ to consst of se-ren members, and to include further any member of the Adtior~ Committee not otherwise a member of the executi~e committee but residenb in or near Wash@on and gi-r@ his time wholly or chiefly to the special work of the committee. The present organization of the executive. committee is as folIows: PJosephS. -4mesl Ph. D., chairman. Datid W. Taylor, D. Eng., secretary. George K. Burgess, Sc. D. Commander Jerome C. Ehmsaker, Vnited St tites 3TZVY. Charles F. Martin, N. E. Naj. Lawrence W. 3fcIntosh, United States *Y. Rear Admiral ViTdiam A. Xoffet.t, United States Navy. Naj. Gen. Mason M. Patrickl United States Army. S. W. Stratton, Se. D. Charles D. WaIcoth Sc. D. OrviLle Wrighi, B. S. . The executive committee, in accordance with the general instructions of the .%drisor3- Committee, exercises the functions prescribed by lam- for the v.-hoIe committee, whninisters the affairs of the committee, and exercises general supervision over all its mtivities. The execut i-re mmmitt ee holds regular monthly meet ~~s. The executive committee has organized the ~ecesmry clerical and techuical staffs for handling the -work of the committee proper. General responsibility for the execution of the programs and policies appro~ed by the exccuti~e committee is vested in the executi~e officer, Mr. George W. Lewis. In the subdi-i-ision of general duties h(’ has immediate charge of the scientific and technical -work of the committee, be~~ &rectIy responsible to the chairman of the executive committee, Dr. Joseph S. Ames. The assistant secretary, Mr. John F. I’ictory, has charge of administration and personneI matters, property, and disbursements, under the direct control of the secretary of the committee, Dr. David W. TayIor.

SUBC03LlIITTEES.

The executi~e committee has organized six standing subcommittees, &tided into two classes, administrate-re and technical, as follows:

C+overnmental relations. Aerodynamic-s. Publications and intelligence. Power plants for aircraft. PersonneI, buildings, and equipment. Ma~erials for aircraft.

The organization and work of the technical subcommittees are co~ered in the reports of those committees appearing in another part of this report. A statement of the organization and functions of the administrative subcommittees follows:

COMMITTEE ON GOVERNMliNT.kl.J RELATIONS. FUNCTIONS. 1. Relations of the committee with executive departments and other branches of the Government. 2. Cio-rernmental relations with civil agencies. ORGAWZATIOX. Dr. Charles D. Walcott., chairman. Dr. S. W. Stratton. John F. Victory, secretary. 4 REPORT NATIONTAL ADVISORY C“ONIMITTEEFOR AERONAUTICS.

COMMITTEE ON PUBLICATIONS AND INTELLIGENCE. FUNCTIONS. 1. The collection, classification, and diffusion of technical knowledge on the subject of aeronautics, including Lhe results of research and experimental work done in all park of the workl. 2. The encouragement of the study of the subject of aeronautics in institutions of learning. 3. Supervision of the Office of Aeronautical Intelligence. 4. Supervision of ~he committee’s foreign office in Paris. 5. The collection and preparation for publication of the technical reports, twhnical notes, and annual report of the committee. ORGMWZATION. Dr. Joseph S. Ames, chairman. Prof. Charles l?. Marvin, vice chairman. Miss M. M. Muller, secretary,

COMMITTEE ON PERSONNEL, BUILDINGS, AND EQUIPMENT. FUNCTIONS. 1.. To handIe aH matl.ers relating to personnel, including the employme~t, promotion, discharge and duties of all employees. 2. To consider questions referred to it and make recommendations regarding the initation of projects concerning the erection or alteration of laboratories and the equipment of laboratmriw md offices. 3. To meet from time to time on the call of the chairman, and report its actions and recommendations to the executive committee. 4. To supervise such construction and equipment work as may be authorized by the tiYecu- tive committee. ORGANIZATION. Dr. Joseph S, Ames, chairman. Dr. S. W. Stratton, vice chairman. Prof. Charles F. Marvin. Dr. David W. Taylor. John F. lTictory, secretary. . QUARTERS FOR COMN~TTE1l.

The he~dquarters of the National Advisory Committee for Aeronautics are located in the Navy Building, Seventeenth and B Streets NW.l Washingtonl D. C,, in close proximity to tho Army znd Navy Air Services. In ApriI, 1923, the committee’s offices were moved from the seventh wing, second floor, to the third wing, third floorj of the hTavy Building, pursuan~ to assigmnent of office space by the Public Buildings Commission. The adnlinist.rative office is also the headquarters of the various subcommittees. The scientific investigations authorized by the committee are not all conducted at the Langley MemoriaI Aeronautical Laboratory, but the facilities of other governmental laboratories and shops are utiIizecl, as well as the laboratories connected with institutions of learning whose cooperation in the scientific study of specific probIems in aeronautics has been secured.

THE LANGLEY MEMORIAL AERONAUTICAL LABORATORY.

The greater part of the research work of the committee is conducted at tha Langley Memo- rial Aeronautical Laboratory, which is located at Langley Field, Vs., on a plot of ground set aside by the War Depiu%ment for the use of the committee when Langley Field was originally iaici out. LangIey l?ieId is one of the most important and best equipped stations of the Army Air Service, ciccupying about 1,650 acres and having hangar and shop facilifiies for the accommo- dation of four bombing squadrons, a service squadron, a school squadron, and an airship squadron. REPORT NATIOhTAL ADT7=ORY C031MITTEE FOR AERONAUTICS. 5 —

In the committee’s laboratory and an the flying field used in connection therewith, the fundamental problems of scientific research recommended by the various subcommittees are investigated. The laboratory is organized with five subditiions, as follows: Power plants division, wind t.un~eI division, fiighh test di-rision, technical service division, and proper~y and clerical division. The administration of the laboratory is. under the immediate direction of the en=tieer in charge, under the general supem-kicm of the officers of the committee. The laboratory consists of six units: A research Laboratory building, containing the administrative offices, the drafting room, the machine and woodworking shops, and the photographic tmd instrument laboratories; two aerodynamical laboratories, one containing a wind tunnel of the open type, and the other a compressed-air wind tunneI, each unit being compIete in itself; two en.he dynamometer laborat vries of a semipermanent tiype, both equipped to carry on investigations in connection with power pIa~ts for aircraft; and an airplane hangar equipped with a repair shop, dope room, and facilities for taking care of 16 or 1S aiq$anes.

OFFiCE OF AERONAUTICAL!NTELU~ENCE.

The Office of Aeronautical Intelligence was established in the early part of 1918 as an integral branch of the committee% activities. ils functions are the collection, classification, and diffusion of te&nicaI knowledge on the subject of aeronautics to the MiIitary and hTaval Air Ser-rices and ci-r-il agencies int crested, including especifly the results of research and experimental work conducted in all parks of the -world. It is the officially designated Government depository for scientific and technical reportis and data on aeronautics. Promptly upon receipt, alI reports are analyzed and classi~ed, and brought to the special attention of the subcommittees having cognizance, and to the attention of other interested partie+ through the medium of public and confidential bulletins. Reports are duplicated where practicable, and distribufied upon request. ConEdential btiekins and reports are not circulated outside of go~ermnent aI channeIs. To efficiently handle the -work of securing and exchanging reports in foreign countries, the committee maintains a technical assistant in Europe, with headquarters in Paris. It is his duty to personally -risit the Government and pri-rat-e laboratories, centers of aeronautical information, and private individuals in England, France, Italy, Germany and Austria, and endeavor to secure for A.merit a not only printed matter which would in the ordinary course of e-rents become avaiIabIe in this country, but more especially to secure ad~ance information as to work in progress, and any technical data QOt prepared in printed form, and -which would otherwise not reach this country. The records of the office show that durirg the past year copies of technical reports were distributed as fol.Io-ws:

{Uotittee md*wbmtittee membe~...... -- l,6i6 Lmgley3femotil .4wonautica1 Labomtory ------1,s35 P&office ofcotittee ------4,35(I Army .fi Semice ------2,351 Nal-~tiSm~ce,ti~ubgM2tie CoWs------4,381 31mdwtwm ------6,171 EducatiomI titititions ...... - 4,77S . Bwwuof Stindmds ------879 mvkaw ------10,49Q

Totifitibution ------36, S70

The abo~e fi=wes include the distribution of 15,262 technical reports, 10,036 technica~ notes, and 21262 technical memorandums of the ATationaI Advisory Committee for Aeronautics. — Two thousand nine hundred and fifty-six written requests for reports were received during the year in additio~ to innumer~ble telephone and personaI requests, and 18,51A reports were for- -warded upon request. 6 REPORT NATIONAL ADVISORY COMLMITTEE FOR AERONAUTICS.

CONSIDERATION OF AERONAUTICAL INVENTIONS.

The committee examines and reports upon all aeronautical inventions which tir(’.submitted to it for consideration and recommenclaiion. By virtue of a formal agreement with the Navy Department, in~entions of a genmd character relating to aeronautics which are received in the ATavy Department are refwre(d to &J National Advisory Committee for Aerommtics for consideraiicm and proper action, The cwl- mittee examines such inventions, conducts the necessary further correspondence with tltr inventors, and where a given invention has prospective value the committee makes a report to the N&vy Department, a copy of which is sent tw the Army Air Swvice. In like manner, aithuug]l without w formal agreement> the committee considers inventions referred to it b! ~he .irmy .Iir ,Service, and if any such inventions appear to be prwnisingf a copy of the committee’s report to the -&my is sent to the hTaTy in each case.

USE OF NONGOVERNMENT.4L AGENCIES.

ll~e various probIems on the committee’s approved research progwns are as a rule assiglwi for studj7 by go~ernmenta~ agencies. In cases where the proper study of a problem requires thr use of facilities not available in any governmental esttiMishn~ent, w requires. the talm h of mcn outside the (krrernrnent service, t“he committee contrtic ts directly with the institution or individual best equipped for the study of each such problem to prcp~re a special repur~ on the , subject. In this way the committee has marshaled t,he facilities of cducat.ional institutions tmd the services of specialists in the scientific study of the problems of flight.

COOPERATION OF ARMY AND NAVY.

Through the personal conttict of responsible officers of the Army and Navy serviug on tile three standing technical subcommittees, a knowledge of the aims, purposes, and needs of ench service in the field of aeronautical research is made known to the other. l’he cordial relations Lhat invariably flow from such personal contact are supplemented by the technical information service of the committee’s Office of Aeronautical Intelligencel which malies mvaiIable tJle latest technical information from aIl park. of the worId. While a healthy rivalry exists in wrhlin respects between the Army and Navy, there is at the same time a coordinaticm of effort iu experimental engineering and a mutual understanding that is productive of the bcsi results. The Army and Navy Air Services have aided whenever caHed upon in every pracf icablc way in the conduct of scientific investigations by the committee. Each service has placed at at the disposal of the committee airpIanes and engines required by the committw for research purposes. The committee desires to record its appreciation of the cooperation given by the Army and hTavy Air Services, for without this cooperation the committee could not ha~c+un(ler- taken many of the investigations that have already made for substantitil progress in aircrtift development. The committee desires especially to acknowledge the many courtesies extended by the Army authorities at Langley Field, where the committee’s laboratories are located.

INVESTIGATIONS UNDERTAKEN FOR THE ARMY AND THE NAVY.

As u rule, the technical subcommittees, including representatives of the Army and Navy ilir Services, prepare programs of research work of general we or application, and these programs, when approved by the National Advisory Committee for Aeronautics, furnish the problems fur solution by the Langley Mernoritd Aeronautical Laboratory. The cost, of this work is lx-me by the committee out of its own appropriation. If, however, the Army Air Ser~ice or tlm hTaval Bureau of Aeronautics, desires specific in-restigations ~U he undertaken by the committee for which the commit~ee has not the necessary fundsj the committee’s regulations as approved by the Presidentj provide that the committee may undertake the work at the expcme of either the Army or the hTavy. The investigations thus undertaken by the committee during the pas~ yew maybe outlined as follows: REPORT NATIONAL ADTISORY COMMITTEE FOR ARRONAUTCICS. 7

FOR ‘THE Bm3RAU OF AEROXAUTTCS OF THE NAVY DEPAR’I’XENi. DewJopment of Roots type superc.h~ger, incIuding the design, construction, testing, and de-reIopment. of the Roots type supercharger for application to the TS and DT airplanes. Investigation in free &Dht of the comparative stability, controIIability, and maneuverability of several types of airplanes, imduding the VE-TJ the SE–5, the Fokker D–VII, the Spad VII, and the MB–3. I~wstigation in free flight of the eflect of dihedral angle on lateral controllability. Investigation and development of a solid-injection type of aeronautical engine. F~~ht. tests of BR–1 racer, including performance tests, with a vie-w to obtaining information for making any changes in the aerodynamic properties of the airpkme that may be found desirable. Investigation of fdcing off and landi~~, including the determination of the air and water speed and the angle of atttick, on la~ding, of -rarious hypes of Seaplanes. Investigation of the pressure distribution over the C-7 airship, irduding flight tests to determine the pressure distribution o~er the envelope and the fins and rudders; teds in the compressed-air wkd tunnel on a model of the (P7 to check the Mormation obt~~ed ~ free tligght; and a study of the equipment and installation necessary for the determination of the pressure distribution over the control surfaces and envelope of the U. S. S. Shenandoah. Investigation of landing on the U. S. S. Langley, includiq the development of instrument; for the determination of the decderations and speed of a.n airplane -when landing on the Langley. Flight tests of superchargers, inchding Bight and performance tests of the DH-! artd DT airplanes equipped with Roots type superchargers, and of the TS airplane equipped with a supercharged Lawrance J–1 air-cooled engine. FOR ‘l?HE EXGIXEERLVG DICISIOX OF THE ARMY AIR SERVICE. FuI1-scale investigation of different wings on the Sperry messenger airplane, incIuding flight tests of six different sets of w@, each to be flown at about six air speeds; hwestigation of the efficiency of propellers when used in front of obstructions as found i~ lmmbi~~ airplanes, includ~~ tests at Stanford University on models of bombamhnent airplanes tested with four different arrangements of propeller with thick W@ section, engine hom=ing, and r~diator; Report on ~he determination of the characteristics of the pressure distribution 0-W%the surfaces of the Thomas Morse airplane under -mcious conditions of ~~ht. In addition to the in-resti@ions enumerated above, theoretical investigations were undertaken for the Army and the Navy, first cm the design and calculations of the Na~ riggd airship U. S. S. Shenandoah, formerly known as the ZR–1, and second, on the Army semi~mid airship RS–i. These inwdiga~ions are more fuHy described under separate headings.

SPECLAL COMMITTEE ON DESIGN OF NAVY RIGID AIRSHIP ZR-L A complete report prepared by the special subcommittee on design of Navy rigid airship ZR–I has been submitted by the National Advisory Committee for Aeronautics to the Bureau of Aeronautics, ~aw. The repor~ contains a complete analysis of the methods of calculating stresses in airships; a discw=sion on the proper ales@ for horizo~tal and vertical b and contro~ surfaces; analyses of maximum unit stresses and factors of safety in lo~~itudinal girders} transverse frames, and shear wire-s. In aJI twenty-se~en appendices mere prepared in addition to the main report. The speciaI subeotittee on design of ~avy rigid airship .ZR-l was appointed by the Nat io na~ Adtisory Committee for Aeronautics at the request of the Bureau of Aeronaut its: of the h’a~ Department. The committee w-as organized as foIlows: Henry Goldmark, chairman. W. Ho-rgaard. L. B- !Ilmkerman. Max M. lfunk. W. Watters Pagon, secretwy. 8 REPORT NATIONAII ADVISORY COMMITTEE FOR AERONAUTICS.

The first meeting of the committee was held in Washington, June 19, 1922, and was called to order by Rear Admiral D. W. Taylor, United States Navy, a member of the N’atiorial Advisory Committee for Aeronautics who outlined the purpose and scope of the special commi~tee’s work. Most of the meetings of the commitke were held in Washington, the committee visiting th Naval Aircraft Factory, Philadelphia; the Naval Air Station, Lakehurst, N, J., and the Bureau of Standards. The summary of conclusions contained in the report of the committee is as follows: (1) The only wise policy was followed by the Bureau of Aeronautics in basing the design of the ZR–i on that of a successful airship while checking its strength by detded computations. (2) The German airship L-49, selected as the prototype, was more suitable than any other, a-s it embodied the most extended available experience with rigid airships. (3) The modifications made in the details were based on sound considerations, and add materially to the strength of the ZR–I. (4) The external Ioading assumed in the calculations is more nearly correct ihan thah used in previous airships, especially the dynamic loads which were derived from special studies m ado in connection with this design. (5) The stress analyses, given in the Design Memorandal are founded on sound principles and form a more complete treatmenfi of the stresses in rigid airships than any hither~o published. (6) With the modifications described in the report, the ‘(method of bending moments” is a satisfactory method for finding the primary stresses in the longitudinal girders. (7) The calculations for determining the stresses- due to gas pressure, ancl the secondary and other minor stresses are also correct within reasonable limits. (8) The maximum unit stresses, while relatively higher than those used in steel structures, correspond to factors of safety, -which have been found entirely permissible in successful aircraft. (9) The fins, rudders and elevators are fully as strong as those in the L-49 and similar airships. (10) The gas ~aIves are of proper size to prevent unduly high pressures under all operating conditions. (11) Excessive differences in air pressure within and without the ship are fully guarded a,gainst by ample openings in the outer enve~ope, with automaiic covers. (12) Owing to the careful specifications and rigid inspection, the quaIity of the malmrid and workmanship is of an unusually high standard of excellence. (13) As shown by the specimen tensile tests, the duralumin used is of’ a very uniform grade and has the specified strength and ductility. (14) The numerous full-sized girder tests indicate a very uniform arid entirely satisfactory breaking strength. (15) The program of trials and tests is -well conceived and will gi~e much valuable information. It should be fully carried out before the acceptance of the ship. (16) The ZR–1 is shown ?.)y comparati~e calculations to be measurably stronger than the British airship R–38, which failed on a trial trip, while other possible remons for its failure, besides structural weakness, have been guarded against in the Zh’-l. (17) Judging the design of the Zl?-1 as a whole, the committee km been very f;vorably impressed by the thorough studies made by the engineers in charge and the good judgment shown throughout in applying their results and also the great care shown in executing the plans. It sees no reason whatever to doubt that the ZR–I will prove a complete success in service. The success attending the earIy trinl flights of the Zl?-l, subsequently named the U. S. S. flherzandoah, led the National Advisory Committee for Aeronau~ics to extend its congratulations to the Navy. The committee stated that it was--particularly gratified to know that every precautio~ was being ttiken to insure the success of the airship and to demonstrate its efllciency in a carefully arranged program of tests. The committee also stated that the perforrnfince of this airship would be watched and studied by the American people for the reason that it is REPORT NATIONALI ADVISORY COMM~TCEE FOR AERONAUTICS. 9 sum to have a ver-y large effect on the future development of lighter-than-air craft in this country for commercial as weLl as military purposes. The following repIy was received from the Assistant Secretary of the Navy under date of September 22, 1923. “ Sm: Tour Iette.r of September 15, 1923, in which you edend the congratulations of the .National .Advisor.y Committee for Aeronautics on the completion and triaI flights of the airship ZR–i, is gratefully ac~ow~edged. “ I desire to express thro~~h you to the National i4d~isory Committee for Aeronautics my sincere appreciation of the courteous message which -you have expressed in your recent Ietter. I am not unmindftd of the very generous cooperation and valuable assistwme which has been rendered by the NationaI Advisory Committee for Aeronautics in connection -with the buiIding of the ZR–1, and your committee is entitIed to a large share in any. success which may be credited to the Navy Department. “ Will you please extend to the National Advisory Committee for Aeronautics my appreciation of their interest in this work that the Navy has undertaken and express to them my thanks for Lheir counsel arid help. “ Respectitiy, “THEODORE ROOSEVELT. “ Dr. JOSEPH S. AMES, C‘Nafiional Advisory Oomrniffee for Aeronautics, l’la+ing~orq D. (7.;>

SPECLIL COMMITTEE ON DESIGN OF ARMY SEMIRIGID AIRSHIP W-l.

At the request of the Army Air Service, the N’ational Advisory Committee for Aeronautics appointed a special subcommittee to examine znd report on the desi=w and construction of the Army semirigid airship known as the RS-I. This special subcommittee was organized on February 15, 1923, as follows: Mr. Henry Goldmark, New York City, chairman. Prof. Wiiam Hovgaard, Boston. Dr. L. B. Tuckerman, Bureau of Standards. Dr. Max M. Munk, National Advisory Committee for Aeronautics. Mr. W. Watters Pagon, Baltimore, seeretary. The RS–1 is a semirigid type airship, 300 feei in length, 71 feet in diameter, and has a capacity of 700,000 cubic feet. The contract for the desigg and construction of the airship was awarded by the Army Air Service to the Goodyear Tire & Rubber Co. The special committee appointed by the National Advisory Committee is to pass upon the desi== and calculations as prepared by the Goodyear engineers working in conjunction with the emgiueers of the engineering division of the Army Air Sertice.

ilMERIC~lX AEROXAuTICAL SAFETY CODE.

During the year the project for formulating a safety code for aeronautics has made active The work is being pursued according to the scheme of procedure d the American ~~~i~~~ing Standards Committee, which in 1920 reco.@zed the United States Bureau of Standards and the Society of .4utomotive Engineers (Inc.) as joint sponsors for this project. A sec~ional committee to handle the technical work was formed during 1921, and at a meeting heId in New York, September 2, 1921, the permanent. organization of this committee was effected, the officers being: Chairman, Mr. H. M. Crane, Society of .4ut emotive Engineers; vice .ehairmanl Dr. J. S. Ames, National Advisory Committee for Aeronautics; secretary, Dr. 31. G. LIoyd, Bureau of Standards; assistant secretary, ~~r. fith~r Halsted~ Bureau of Standards. The sectiomd committee consist-s of 36 members. The following organizations have representation on the sectional committee: Aero Club of America. Aeronautical Chamber of Commerce. 10 REPORT A’ATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.

American Institute of Electrical Engineers. American Socieky of Mechanical Engineers. American Socieiy for Testing Materials. American Society of Safety Engineers. Manufacturers Aircraft Association. National Aeronautic Association National Aircraft Underwriters Association. National Advisory Committee for Aeronautics. National Safety Council. Rubber Association of America,. Underwriters Laboratories. United States Coast Guard. United States Forest Service. United States Navy Department. United States Posfi (Mice Department. United States War Department. United Stutes Weather Bureau. The American Aeronautical Safety Code will include parts as follows: Introductory Part.-Scope and Nomenclature. Part I.—Airplane Structure. Part 2.—Power Plants. Part 3.—Equipment and Maintenance of Airplanes. Part 4.-SignaIs and Signaling Equipment. Part 5.—Airdromes and Airways. Part 6.—Traffic and Pilotage Rules. Par& 7,—Qualifications for Pilots. Pa.rfi 8.—Balloorw. Part 9.—Airships. Part 10.—Parachutes. These various parts are being developed in working subcommittees. The procedure has been for the subcommittee to me~are and distribute to those interested a preliminary draft for discussion in mimeogp-aph ~orrn. Later the preliminary draft is completely recorisidered together with all criticisms of it which may have been submitted. A revised draft is then reported for the consideration of the sectional committee. The sectional committee has considered six such subcommittee reports and approved five of them for publication. Each is then published in pamphlet form as one of the various parts of the code listed above, and is made available for general distribution, In this printed form the various parts of the code are subject to revision pending their adoption by the sectional committee and sponsor bodies when all parts of the code are ready for consideration together. The stage of development of the various parts of the code is listed below: The Introductory Part, Scope and Nomenclature; Part 1, Airplane Structure; Part 2, Power Plants; Part 6, Traff?c and Pilotage Rules; Part 7, Qualifications for Pilots; and Part 10, Parachutes, are in the form of a preliminary draft. Plans are made for their revision in the near future. Part 3, Equipment and Maintenance of Airplanes; and Part 4, Signals and SignaIing Equip- ment, have been approved for publication by the sectional committee; and Part 5, Airdromes and Airways; Part 8, Balloons; and Part 9, Airships, are available for distributio~ in pamphlet form. 1NTERNATIONALSTANDARDIZATIONOF M’IND-’J!UNNELRESULTS.

The program outlined in last year’s report for the testing of the National Physical Labora- tory airship models has been carried out, and separate reports have been completed and submitted by the Langley Memorial Aeronautical Laboratory, the llassacl~uset~ Institute of REPORT NATIONAL ADVISORY C031XITTEE FOR AERONAUTICS. 11

Technology, the Bureau of Standards, and the aerodynamical Iaborato,ry of the Washington ~avy ~ard. The separate reports have been considered by a committee bomisting of Dr. A. F. Zahm, Prof. Ed-ward P. Warner, Dr. H. L. Dryden, and Mr. D. L. Baco~, and a joint report on the comparative tests of the two models by six American wind tunnels has been prepared. The airship models ha~e been returned to the Nat iomd Physical Labor~tory. Exact copies of the National Physical Laboratory airship models have been made and will be tested in the commitfiee’s compressed-air wind tunnel at Langley Field in the near future. The committee has received from the National Physical Laboratory standard models of ‘ a R. A. 1?. 15 airfofi, which are now undergo~m tests at the Langley Memorial Aeronautical Laboratory. These models have been tested both in England, at the National Physical Labora- tory, and in France, at St.. (&r and Aut.euil (Eiffel). The standardization tests authorized by the Xationd Advisory (lommittee for Aeronau- tics to be conducted in the United States ha~e been partially completed. The models, consisting of three cylinders having length-diameter ratios of 5 to 1, and four models of U. S. A. 16 airfoil section each ha-r& an aspect ratio of 6 to 1 and a length ~arying from 18 to 36 inches, ha-re been tested and a report submitted by the Langley Memorial Aeronautic.al Laboratory. The tests ou both the cylinder models and the airfoiI models were made over as wide a range of V/L as po~~ible, and included determinations of lift: drag: and pitching momenfi every four degrees from – 4° to +20°. As a fist step in a program of further kests, the models have been sent &o the aerodynamical laboratory of the Washington L’avy yard.

FUN) AME??TAL PURPOSES OF THE AIR MAJL SERViCE.

In December, 1922, the Iate President Harding wrote to the ~atiomd Advisory Committee for Aeronautic-s requesting the recommendations of the committee as to the most promising program to be followed by the Air Mail Service in the expenditure of its limited funds. The reply of the committee, as transmitted under date of December 20, 1922j ~as as follows: “DEAR MR. PRESmEN~: In resptmse to -your letter of December 4, I have the honor to submit herewith the advice and recommendations of the llationaI Advisory Committee for Aeronautics as to the most promising program for the Post Office Department to folIow in connection with the Air Mafl Service. “This report contains the views of the committee developed at two speciaI meetings held on December 12 and 20, 1922, grouped under Lb-efollowing topics: “ 1. The fundamental purpose of the Air Mail Service. “ 2. The accomplishments of the Air MaiI Service to date. “ 3. What remains to be ac.compIished. “ 4. Comparison of an operating with a de~elopment program. “ 5. Recommendations of the committee.

“The fundamental purpose of the Air Mail Service is to demonstrate the safety, reliability, and practicability of air transportation of the mails, and incidentally of air transportation in general. In particular, it. shouId— “ (a) Develop a reliable 36-hour service between ~ew l“ork and San Francisco, and make that service se~-supporting by crest ing the necessary demand for it and charging a rate between ordinary postage rat es and &oht-let ter telegraph rates. . “ (h) Keep strict records of the cost of the service and strive in e-wry way to reduce such costs to a rninimuml thereby demonstrating the value of air transportation from an economic point of view, and in particuhw making it possibIe for private enterprise e-wntuaLly to contract for the carrying of mails by airplane at a rate which not only vrould not exceed the ~come from .. such a service but -would permit the Post Office Department. to protide other postal airways to meet the demands of the people for the more rapid transportation of mail. In the present undeveloped state of the art, it would be wholly impracticable to operate an air mail service by contract. 12 REPORT NATIONM-IADVEORY COMMXTEE l?OR AERONAUTICS “2.THE ACCOMPLISHMENTSOF THE AIRMAILSERVICETO DATE. “The Air MaiI S&vice was established in 1918, flying between New I’ork and ~?ashingkm. It is now operating betmeen ITew l“ork and San Francisco, in a system of train-tind-airplane relays, for night and day travel, respec Lively. The safety and practicability of air navigation in the daytime have been well demonstrated by the performance during the past year, when more than 2,000,000 miles were flown in the Air Mail Service without a fatality. This performance over the longest regularly traveled route.in the world is unique for safc~y and regu- larity. Data have been produced as to cost of operation, h t this cost is higher than necessary, because airplanes not specially designed for, nor entireIy suitable to, the service ha~e of neccssi~y been used. ‘%. \~HATREMAINSTO BEAcCOMYLIS~ED. “ The foIlowing very important objects remain to be accomplished by the Air kfaiI Service: ‘‘ (o) Demonstrate that night iiying is practicable over a regular route anfl schedule, This i~cludes development of a chain of emergency landi~g .fieIdsj ~dequate ligh~ing for night flying, improved methods of navigation through fog, storm, and darkness, and a specially trained personnel. “ (6) Bring about the development of an efllcient ~ype of airplane for this specinl purpose, as diskinct from military purposes, and perfect rnekhods for protecting the mail from damage I}cyfire or crash. “4. COMPARISONOFAN OPERATINGWITHA DEVELOPMENTPROGRAM. “ The present daytime air mail service from New Irork to San Francisco, alternating ~vith trains at night, wilI require an appropriatiort of about $1,500,000 a year. The appropriation for the current fiscal year is $1,900,000, of which about $400,000 is being devoted to preliminary preparation for night flying. With an appropriation limited to $1,500,000, [he developtnen t of night flying on the transcontinental route wilI be impossible. If the Air hfail Service were to concentrate on the development of night flying between Chicago and Cheyenne, which is tlw part of the transcontinental route where this should be first attempted, night flying migh~ be de-relopecl with an appropriation of $1,500,000, but the present airphme service from Chicago to h’evv York and from Cheyenne to San Francisco would haTe to be abandoned for 1ack of funds. This wouId be a step backward, would waste the+pr~ent investmen~ in organization and equipment east of Chicago and west of Cheyenne, and would alienate pubIic interest and suppm% “on the other hand, the development of the Air Mail Service over the one auihorizcd transcontinental route, with facilities for Bight flying between Chicago and Cheyenne} wilI, it is estimated, require an appropriation of $2,500,000 for the next fiswd year. In order tha~ facilities for night flying may be extended over the eastern and -western portions of the trans- ccmtinentaI route, the sum of approximately 82,500,000 shouId be appropriated for tlm Air Mail Service for each of the two fiscal years next following. “5. REcOMMENDA~ONSOFTHECOM.MPIYEE. “The National Advisory Committee for Aeronautics submits the foIlowing recommendations: “A. That the Air Mail Service under the Post Office Department be continued until ii has- “ (1) Demonstrated the practicability of night fIying in the mail service, and actually estiabIished a regular service between New I’ork and San Francisco in 36 hours or loss. “ (2) Met the popular demand for a fast transcontinenhd service and made such scr-rice self-supporting by means of appropriate rates; “ (3) Demonstrated the exact cost and economic value of air transportation, using tho most appropriate equipment, including airplanes specially designed for efficient perfcmuancc, “B. That when the above program is once accomplished the further application of aircraft to the carrying of mail be effected by contracts with private enterprise. “C. That, as the development of night flying can not be undertaken on any section of the Nevv I’ork to San Francisco route with an appropriation limited to $1,500,000, an appropriation of betwee~ $2,300,000 and $2,500,000 be granted for the fiscal year 1924 for the Air Mail Service. REPORT NATIONAL ADTTSOFW COLLKKCTEE FOR AERONAUTICS. 18

“D. That if the appropriation for the next fiscal year is limited to $1,500,000, the only thing that can be done is to continue the present plan of flying by day and alternating with trains at night. To so tilt the appropriation as to prevent the inauguration of night fi-tig on the h~ew I“ork to San Francisco route will render the ~alue of the Air MaiI Sem-ice relatively wmd.1 as compared to the great -ralue it v-ould otherwise ha~e. “ Respectfully submitted, ‘( ~TATION.\L .%OVISORYComm’rmm FOR .%IZROXAUTTCX9, “ f2J2kRL.Esl).WAwom, (%z{rnmn.”

Congress appropriated $1,500,000 for the fiscal year 1924, which -ims insticieni to pro-ride for reguIar night flying of the mails. The Post Office Department., how-ever, did manage, with its limited appropriation, to make a five-day tesk demonstration of the practicability of night flying between Chicago and Cheyenne, i~ which the mail was carried across the continent, in each direction in from 27 to 30 hours. b the jud=ment of the Fiational Ad-risory Committee for Aeronautics, that demonstration was the most significant forward step made in atiation in a year marked by substantial progress in many respects. The committee, under date of Septem- ber 13, 1923, addressed the foIIowing letter to the Postmaster General: “ Sm: The executi~e commitiee of the National Adtisory Committee for Aeronautics, Et a regular meeting held on September 13, 1923, had under cons-idemtion the significance of the recent five-day test demonstration of nighi flying between Chicago and Cheyenne by the Air Mail Setice. Our members were very much grati-lied with this important initial success, and adopted a resolution -which 1 ha~e the honor to tranwit.} as follows: “‘ Whereas in a statement deding with the fundament.aI purposes and the most promising program of the Air Mail Service, submitted to the late President Harding on December 20, 1922, the N’atiomd .%dtiory C!ornmittee for Aeronautics stated that one of the important objects to be accomplished by the Air Mail Serrice -was to ‘( demonstrate that night flying —— is practicable o-rer a regular route and schedule”; and “‘Whereas in a recent fi-re-day test demomtration of the practicability of night flying, mails were successfully carried across the contine~t in both directions in less than 30 hours: &row, therefore be it . “ ‘ Re.solwd, That the National Advisory Committee for .keronautics recognizes that t.lie nigh~ fi.tig of the mails between Chicago and Cheyenne on a regular schedule for five days is in itself an epoch-making p erfomuance, and a splendid start toward the accomplishment of one of the fundamental purposes of the Air Mail Serrice--the de-wlopment of a regular and reliable mail sefice b etmeen the MIantic and the PacMc in thirty-six hours or less; and be it further “ ‘Resolved, That the ~ational Advisory Committee for Aeronautics exterids its congratulations to the Postmaster General and to fl ofbials and employees of the Postal Sem-ice on this sigticank achievement. that w-U ha-re far-reaching results, not onIy in t assuring the more rapid transportation of the mails, butt also in stimulating the de-mlop- ment of aviation for cifi and commercial purpmes; in lessening the handicap of natural barriers of distance between different sections of the United States, and in promoting the unity of the American people.’ “Respectfully, “ NATroNAL h~LsoRT COmmr’r EE FOR i!KEROXAGTICS1 “JOSEPH S. AMES, “ G’ltairman, Execvtice Committee.”

The FTational Advisory Committee for Aeronautics at this time reiterates its faith in the value to the Nation of the & Mail Swric.e as a practical means for aiding the development of commercial aviation, as -i@ as a means for expediting the transp orttattion of the maiI.. We ca~ not shut our eyes to the future. Mail is bound to be carried eventually by the fastest means available, and it is safe tcI say that in this age of progress the American people will demand a more or less general use of aircraft in the near future for carrying the reads. 14 REPORT ITATIOI?ALADVISORY COMMITTEE FOR AERONAUTICS,

The ~atiomd Advisory Committee for Aeronautics strongly recommends the granting by Congress of liberal appropriations to the Air Mail Service, sufficient to enabIe ifi Lo— (a) Demonstrate that night flying is practicable over a regular route and schedule. l’his includes development of a chain of emergency landing fields, adequate lighting for night flying, improved methods of navigation through fog, storm, and darkness, and a spccidy trained personnel. (6) Bring about the development of an efficient type of airplane for this special pwpose, as clistinct from military purposes, and perfect methods for protecti~g the mail from damage hy fire or crash. THE NEED OF FEDERAL LEGISLATION.

The committee again recommends the creation by law of a Bureau of Civil Aercmautics in the Department of Commerce for the regulation and licensing of aircraft, airdromes, and aviators, and the general control and encouragement of commercial flying. The increasing relative importa~ce of aircraft in warhzre is alone sufficient to justify the l?ederaI Government in taking proper cognizance of the probIem of commercial aviation and aiding its development. It has been the history of civilized nations that governments have found it necessary and advantageous to aid in the development of means of transportation. The wonderful growth of transcontinental railroads in America was greatly aided by land grfints from our Government. Progressive European nations are spending public funds through dircc~ znd indirect subsidies for the promotion of civil and commercial aviation, It is essential to tho practical development of aviation in America that the Federal Government give inldligerit support and effective aid, through Federal Legislation outlined above, and by cooperation with the States in the establishment of airways and landing fields.

CANADA’S CONTINUED COURTESY 770 AMERICAN AIR PILOTS.

In May, 1920, Canada promulgated regulations permitting United States qualified aircraft and pilots to fly in Canada for a period of six months on the same basis as if the United Sta~es had wtablished its regulations as contemplated under the Convention for the Regulation of International Air Navigation. The Government of the United States has not as yet ratified this convention. Canada, however, has from time to time extended for periods of six months or a year the regulations favoring American air pilots, bhe latest extension expiring May 1, 1924. The Government of the United States has expressed appreciation to the Government of Cannda for these repeated courtesies. The proper remedy for the res-dting unsatisfactory situa~ion is either for the United States to ratify the Convention for the Regulation of International Air Ilavigation or to negotiate a separate treaty with Canada. Neither of three remedies, however, could be effective in the absence of an agency for the regulation of civil air navigation in tih~ United States. The annuaI recurrence of diplomatic negotiations with Canada on this subject serves to emphasize khe need for the enactment of Federal legislation for the regulation of air navigation, which is one of the recommendations contained in the conclusion of this report.

INTERNATIONAL AIR CONGRESS.

.&i lnternational Air Congress, unofficial in character, was held in London in June, 1923, at~ended by representatives of nations interested in aeronautical de-relopment~ including the United States. Without going into the details of the transactions of the congress, the cmnmittee deems it of interest to present a digest of the resoluiiom which were advpted. The most important resolutions confirmed were those dealing with international air lines and the demands made by flying on the human frame. The first, put forward by Spain, Rumania, Holland, Norway, Italy, and Belgium, at a meeting under the presidency of France, urged “ That in the interests of aerial navigation the Governments be asked to unite in sub- sidizing the transcontinental air services as speedily as possible. ” The second resolution -was that “From the evidence rLow accumulated of the physical condition of pilots who have flown for years the medical section of the International Air Congress affirm that, given reasonable fIying hours, they have no evidence to show that piIots deteriorate REPORT NA~ONU ADVISORY C03~D~E IOR AERONA~GS. 15 more rapidly than in other employments, and the data and curves already a-railable indicate that these pilots maintain a condition above the normal for their age.” The remaining resolutions confirmed ~ere as folloms: “The International Air Congress of Aerial h~atigabion urges the International Cornmksiort for Air Navigation to evolve some uniform scheme of posting the weather forecasts in all air stations, and of compiling a ieafiet of essen~ia.1adtices to be handed to piIots. “ That as soon as possible an International Conference be held, with delegates appointed by their respecti~e Governments, to study and define the generaI principles of private international law relating to the airt and to submit propositions of law for ratification by the -t-arious nations concerned. “That this International .&r Congress in-rite the International Commission for .kir hTati- —— gation to consider ihe advisability of setting up a permanent international commission for the standardization of aircraft materials and component, parts, and for this purpose to invite delegates from the ~arious nafional standards organizations to report on the mattier. “ That the International Air Traffic Association shouId be imited to approach the postal authorities of the various European Go~ernments with a tiew to discovering the air tram~port time-tables which would best suit them for the carriage of mails, and this body should then communicate this information to the various air transport companies concerned.”

REPORT OF COMMITTEE ON AERODYNAMICS.

ORG.CZZ4TIOX.

The committee on aerod~namics is at pres~fi composed of the f~~o~ng members: Dr. Joseph S. Ames, Johns Hopkins University, chairman. Mr. D. L. Bacon, LangIey MemoriaJ Aeronautical Laboratory. Dr. L. J. 13riggs, Bureau of Standards. Mr. H. ~. Eaton, Bureau of Standards. (%nmander J. Cl. Hunsaker, United States IVavy. Maj. Leslie MaclMI, United States Army, engineering div-kion, McCook Field. Lt. C. FT.Monteith, United States Army. Prof. CharIes F. Mm-in, Chief, Weather Bureau. Prof. Edward P. Warner, Massachusetts Institute of Technology, secretary. Dr. A. F. Zahm, United States Navy.

FUNCTIONS.

The functions of the committee on aerodynamics are as follows: 1. To determine -what problems in theoretical and experiment aI aerodynamics are the most important for in-restigation by governme~tal and private agencies. 2. To coordinate by counseI and suggestion the research work involved in the in~estigat.ion of such problems. 3. To ack as a medium for the interchange of information regardhg aerad.ymmic imzsti- gations and developments in progress or proposed. 4. The committee may direcfi and conduct research in experimental aerodynamics in such laboratoW or laboratories as may be placed either in whole or in part under its direction. 5. The committee. shaII meet from time to time on the caII of the chairman and repmt its action and recommendations to the executive committee. The committee on aerodynamics by reason of the representation of fihe ~afio~ organizations interested in aeronautics is in close contact with all aerodynamicaI work being carried out in the United States. In this -way the current work of each orgmization is made known to all, thus preventing duplication of effort. Also all research -work is stimulated by the prompt distribution of new ideas and new re.suIis, which add greatly to the efficient conduction of aerodynamic research. The committee keeps the research workers in this country suppIied with information on alI European progress in aerodynamics by means of a. foreign represent ati-i-e who is in close touch with alI aeronautical acfiitities in Europe. This direct information is 16 REPORT NATIONAL ADVISORY COIWKKE=3 FOR AERONAUTICS. supplemented by the translation and circulation of copies of the more important foreign reports and articles. The aerodynamic committee has direct control of the aerodyna.mical research conducted at Langley Field, the propeller research conducted at Lel and %anf ord University under the supervision of Dr. W. l?. Durand, and some special investigations conducted at the Bureau of Siandards and ai a number of the uni-rersities. The investigations undertaken FLt.t.ho Wash- ington liTavy ‘yard aerod,ynamical laboratory, the engineering division, Army Air Servicej [he Bureau of Standards, and the Massachusetts Institute of Technology are reported to the committee on aerodynamics.

THE LANGLEY MEMORIAL AERONAUTICAL LABORATORY. Wind funnel researclt.—Mandardiza fion.-Following a policy unanimously subscribed to by the aeronautical laboratories of the worhl, the committee is sponsoring a series of tests in the chief wind tunnels of this country> with the object of siandardiz~ng apparatus to a point which wilI permit the intercomparison of daia. To this end se-reral groups of models, comprising wings, circular cylinders, and airship models, ha-m been teste.cl in the atmospheric wind tunnel ancl are now bsing circulated among the other importank wind tunnels of this c.oun~ry. This program has been combined with that of the British Aeronautical Research Committee to the exten~ of substituting the British airship models for the American, and by circula~ing the single BriLish airfoil, together with the four American ones. In conjunction with the standard tests, certain special investigations of turbulence eflcct and of model support interferences have been made which> it is expected, will be. of usc in interpreting the collected data resulting from tests of the standard models in numerous laboratories. Aiq$oiki.-Routine tests ha-ve been made of a number of propeller airfoik at the requmt of Stanford University. Thcso airfoils had previously been tested in another laboratory in which the speed was limited to 30 m. p. h. Our low speed results were in substantial agreement with these, bu~ the influence of scale on these partictdar models was so great as to show an entirely different set of characteristics at 67 m. p. h. and prov-ided another example of the extreme desirability of high scale testing. The division of load between the individual wings of biplane and triplane combinations is being elaborately studied at the request of the Bureau of Aeronautics, in order to permit of more intelligent design of wing structures, particularly those intended f or Iarge airplanes c arrying heavy loads. The very large number of possible wing arrangements considered in the program of tests have required the exclusive services of the atmospheric wind tunnel and its staff on this work for many months. The previous determinations of pressure distribution o-rer airfoils are being extended by measurement on a new series of thick tapered wings proposed by the Air Service, models for which are in preparation. In order to expedite the test work, and thus minimize the monopoIy of the tunnel by this one in~estigationl a method has been devised -whereby aI1 necessary pressure measurements on any one model may be made in an hour, instead of the day or more which was former~y required. This method involves the connection of a large number of pressure ope~ings on the model surface through a system of hypodermic tubes, embedded in the model, to a multiple manometer, where the pressures are simultaneously recorded. The saving of time required to make the tests more than offsets the extra cost of the construction of the models. Modez airplanes.—A complete model of a thick wing biplane, the Fokker D–VII, has been subjected to tests in the atmospheric and variable density tunnels. The former tests were limited, of necessity, to one-tenth of full dynamic scale, while the latteT were carried to more than five times that value by increasing the density of the air. These experiments, in conjunction with flight tests, demonstrate that whereas the atmospheric tunnel gives a good index of full scale performance with airplanes using thin wings, it can not be considered to give a reliable ~ indication of the full scale drag of thick-winged airpIanes, In this particular case the atmospheric tunne~ shows a maximum lift/drag ratio about 20 per cent lower than does the mriablf density tunnel in agreement with flight tests, ILEPORT NATIONAL ADVISORY COMMITI!EE FOR AERONAUTICS. 17

A model of a muItipIane pursuit airplane -was tested in the atmospheric tunnel at the request of the Air Service. This test was of interest chiefly because the extremeIy low scrde of test, necessitated in any ordinary tunnel b-y the wing chord of 0.8 inch, made the result Dot directly applicable for desigg purposes and demonstrated that. the only way to acquire usabIe e.xperi- mentaI data on such a modeI WW be by means of the variabIe density wind tunnel. Flight research—Airtships.-To permih a rat ional basis for stress analysis, and at the request of the Bureau of Aeronautics, an axtensive study is being made of the air forces which act upon the huII and control surfaces of a nonrigid airship in flight. After some prehfiary tests with instruments already on hand, Dew measuring instruments were designed and constructed which permi~ the simu.Itaneous measurement at frequent intervals of 240 different pressures. Some rough preIimi_nary estimates of forces on the control surfaces were communicated to the h7avy before the first flights of the Z12-1 (rechristened U.S. S. S7wnandoah). Since then a tremendous amount of data has been accumulated from these tests, the computation and anaIysis of which wi.U occupy all avadable personnel for several months to come. The experience gained during the progress of this work is now behg app~ed ~ a caref~ ~alysis of the larger Problem Of determining the loads on the U. S. S. Shenandoah. Airptanes.-Pressure measurements on airpIane wings ha-i-e usually been limited to model tests, or to measurements over a very small portion of an airplane wing in flight. The Laboratory has recently completed an eIaborat-e series of measurements over the entire wing surface of a high-speed pursuit biplane in noimaI flight and during vioIent maneuvers for the engineefig division Army Air Service. The results of this research throw a new light on the constructional desiderata of fast airpIanes, as several small areas were found on ~hich the air suction was many times greater than that. usually assumed for the design of the structure. This information gives an explanation of the cause of se~eral accidents to racing and pursuit airplanes which could not be explained before. The previous investigations of dynamic stabiLity have been extended by determination of the period of longitudinal oscillation and the longitudinal damping characteristics of two airplanes, using both free and Iockid contro~. Only one instance of d-ynamic instability mas observed and it is concluded that the study of this characteristic need nob be performed on modeIs of new airplanes but may safeIy be postponed until these airplanes are a~ailable for tligghttests. PreIimina~ experiments have been made on several airphnes to determine the maximum lift coefficient which those airphnes can be made to dedopl how nearIy this lift coefficient can be approached in level flight, and what margin of controI is a-railab~e under these conditions. At the request of the h’avy, the Laboratory is in_res&~ating the pIaning characteristics of seaplanes moving on the surface of the -water, in order to acquire data previously obtahabIe only from the model basin. Propellers.-The committee is conducting, this year for the first time, f&ht tests of propellers. The usual assumptions for the computation of slipstream velocities in performance estimation have been verified in flight and, from the -velocities so measured, an approximation of the effective thrust has been de-reIoped which is in cIose agreement with the tlgures obtainable from known rztes of gIide and chm.b. Preparations are in progress for tlighti tests, in conjunction with compIete model tests at Stanford Llniwmity, of two families of propellers having varying pitch ratio and aspect ratio, respectively. NTO&mht researches on systematically varied propellers have ever been made in paraLIeI with mind tunneI tests of the same propellers, and this research is expected to .fl a long-felt need. Air sfructure.—The theory of dynamic similitude as applied to aircraft is based on the assumption that an airplane and its modeI prototype both move in fluids having equivalent initial disturbances. Experiments performed at the laboratory with large spheres falbg from a great height in cabn air have shown th~t the. air resistance coefficient of a bhmt body in the free atmosphere may be quite difierent from that of the same body in any known form of wind tunnel End that this dka=~eernent is apparently chargeable to “ air structure.” While the flow about blunt bodies is undoubtedly dependent. upon the nature of the initial air structure 18 REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. to a much greater degree than is thtit about thin airfoils, we have reason to believe that airship hulls and some of the thiclier airfoils have resistance coefficients which, for small Reynolds numbersj depend fully as much on initial air structure as they do on the c1ynamic, scale of motion. These experiments, begun on spheres, are to be ccmtinued with other bodies in order to gain additional information on this important matter. Performance iesik.—h addition to its regular research work and because of the accurate special instrument and the experienced personnel avaiIable, the laboratory has been requested to make an accurate measurement of the performance of several airplanes. This has involved a study of the comparative merits of different means of measurement and methods of reducing flight. data for compariso~. A proper application of the appro~ed method serves to obtain more consistent data than that usualIy tesulting directly from the performance tests. Further progress has been made on the investigation started se~eral years ago, to compare the merits of a series of airfoils, as determined in the wind tunnel and in actual flight. Thesa experiments were start ed on the thin-wing J&T4th and continued on the thick-wing 11’okker D-VIII but the engineering division of the Army Air Service is now furnishing the committee with a Messenger airplane having six sets of interchangeable wings of different profiles, and with an exact model of the airplane, The scale intermediate between the corrwmtional wind tunnel and flight testing is now bridged by means of the variable density tunnel, thus permi~ting direct comparison between tunnel and flight tests, so far as the influence of th~ viscosi~y is concerned. Wind iummel and jliglii equipmenf.—The atmospheric wind tunnel has been in continuous operation throughout the year, and all difficulties with both the electrical inst tillation and the aerodynamic characteristics of the tunnel, which had at one time or another CMEXX1inter- ruptions to the regular routine of work during pre~ious years, ha-re now been overcome entirely, A minor improvement has been effected by the provision of air vents or ‘(bleeder” holes communicating between the operating chamber and the tunnel proper at a point WW down stream from the model. These prevent distrubances near the model due to the inevitable air leak which must occur through the walls of the operating chamber, The N, A. C. A. variable density wind tunnel has been continuously developed cluring the year and is now sufflcient,Iy refined and accurate. This turmeI was the first one of its kind to be constructed and required many details in design where no precedent was availabIc. Many minor details of the operating and observing devices_ were therefore installed merely in a temporary manner until they should prove their usefulness or satisfactory operation under test. After actuaI operating experience with the tunnel. these devices ~lave either been made permanent, or have been so changed as to permit sufficient convenience in operation. The air flow has been greatly improved by installing deflector plates at both ends of the air tank and a honeycomb at the entrance to the throat and is no-iv satisfactorily uniform, At the time of the first tests the provisions for mechanically changing the attitude of the model were not yet completed and experiments were hampered by the necessity of detlating the tank between successi~e measurements. The mechanism to avoid these troublesome delays has no-iv been installed and the instrumental equipment has been augmented by remote control micro-manometers and air pressure distributing valves which permit of measuring successively a number of pressures on a single instrument. The electric-power transmission line from Hampton to Langley Field, which has until the present time been of insufficient capacity to permit the simultaneous operation of both wind tunneIs} is now being replaced by one of larger capacity and no further inconvenience from this source is anticipated. lnshw--ent research and development, —During the past year the standard recording instruments have been improved in many respects and have been appIied to new uses. In addition, several new types have been developed and puti into successful operation. The three component and single component acce~erometers have undergone changes making for easier adjustment of sensitivity and damping. The singIe component turn meter has been redesigned, using a standard commercial gyroscope, and its sensitivityy range has been increased. A speed REPORT! NATIONAL AWISORY COMMW13?-E FOR AERONAUTIC% 19 change mechanism has been built for use in the recordi~r instruments, which provides six Hrn speeds ranging from one revolution of the drum in one-half minute to one in two hours and thus covers the range from rapid maneuv-ers to ce~~ tests of airplanes. A new constant speed motor has been de~eloped for general instrument application, which is both ~~ht er and smaller than the older type, and is also more efficient. Considerable work on sensiti~e presswe capsuks has been done in the laboratory and se~era.1 very small and efficient capsules produced, some of which are especially =well adapted for the accurate record@ of smalI pressures such as those encountered on the surface of an airship. The pressure instruments, such as the air-speed recorder, ha-re been adapted to other uses. One of these new applications is the recording of small changes in altitude, for which purpose — a combined air-speed mete-r and statoscope us~m two small sensitive capsuks has been developed. An air-speed recorder having a ~ery stiff diaphragg has been used with a water Pitot for measuring the water speed of seapIanes. The air-speed recorder has also been used for measuring the ground speed of an airplane in taki~~ off and Ianding, by record@ the pressure impuIses produced by a piston and cylinder operated by a earn on one of the airplane wheels. A new trailing bomb-shaped instrument has been developed to replace the bomb &mo- graph. The case contains a penduIum -whose position with respect to the axis of the bomb is determined by means of a rolling cent act and resist ante, the records being made in the cockpit of the airplane instead of in the suspended instrument. The advantages of this type am greater ease of handl@ and independence of sunlight for recordi~~, permitt&m test flights on duU days and in any direction. A combined air-speed and altitude recorder was dewloped primarily for hhe supercharger flight work but has proved valuable for other flight work as well. It is a standard type of recorder, hawi~~ an air-speed capsule and a barometric ceII, both giving a continuous trace on the film. An automatic observer has been constructed for the high altitude superch~ger flight work, which consists of a box carrying an electrically operated multiple camera and lights at one end and a panel of indicating instruments at the other end. W%h this apparatus a picture of 8 or 10 indicating instrumen~ dials is made every 20 seconds, standard moving- picture film being used. A combined air-speed and inclination recorder has been built for use in glide tests and other investigations requirii a record of the airplane’s inclination. The inclinometer com=ists of an oiIdamped pendulum carry@g a mirror which controls the recording Iight beam. A motor driven micromanometer with a capaeit y of 40 inches of pressure head has been designed especially for use in the variable density wind tunnel. This manometer, however, wiIl also be of considerable wdue for the accurate and rapid calibration of pressure instruments in the laboratory. A new suspension type oil-damped galvanometers has been built for use with the electrical recording instruments. It has a period of approximately one-hundredth of a second and wilI eliminate the various difficulties encountered with the commercial movements formerIy — employed. h addition to the above major items a considerable number of the simpIer instruments and accessories have been built, such as yaw heads, Pit ot tubes, swiveling air-speed heads, manometers, and various indicati~w devices.

AERODYNAMIC TED30EY.

Dur@~ the past year aclditicmal impro~ements have been made in the theory of air forces, brh+& the general theory to a point where additional research -work appears necessary before further important progress can be made. In particular, that part of the theory which pertains to wings and W@ sections in a nonviscous fluid has been very much elaborated and the methods of study reduced to f ormuke as simple as those employed in other branches of technical science. A notable advance was made in the theory of air forces on the hulls of rigid airships as worked out by Dr. Max M. Mnnk in connection with the report of the ZR–I committee. Pre- liminary experiments have veritled this theory in a satisfactory manner. IL is proposed to 20 REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. improve and extend the theory to make it ~ppIicable to semirigid and nonrigid airships which, in consequence of their small fineness ratios, prese~t considerable difficulty in the exact calculations of the air forces involved. Doctor Munk recently devised a new method for use in computing propeller characteristics and assisting in the choice of the proper propeller. An important innovation suggested by this method is the use of certain new coefficients which bear simple and direct relations to the principal propeller characteristics, so that the design work is considerably simplified. The new method has been checked by analysis of more than 150 tests on models and in free flight.

STANFORD UNWERSITY.

The propelIer investigation, mentioned in last year’s report, to determine the thrust and torque coefficients and the efficiency with obstructions placed in the air stream, hs,s been completed and a report submitted. In this investigation simple geometrical forms were selected for the obstructions, such forms offering the advantage of easy, exact reproduction at another time or in other laboratories. An extension of the investigation of propeller interference is being conducted, using obstructions of various forms as encountered in actual airplane design, especially such designs where the propelIer is mounted in fron~ of the fuselage or nacelle. The propeIler investigation now being conducted at Stanford University for the committee is on the coefficients of propellers of standard type. In determining coefficients of propellers of standard type an arbitrary standard propeller, designated as propeller C, was selected, the propeller type being one of standard use and found satisfactory. The invest~iation will hiclude tests of 13 model propeIIers, comprising three series of tests, In the first series the pitch will be varied, being changed in steps from 0.5D to 1.lD; in the second series, propeller C wilI be modified by changes in thickness of the blade section; and in the third series, modification wilI be in blade width. The program covering the investigation was prepared under the direction of the subcommittee on aerodynamics and in conjunction with the Bureau of Aeronautics, Navy Department; engineering division, Army Air Service; Langley Memorial Aeronautical Laboratory; and Stanford University.

WASHINGTON NAVY YARD. Wind tunnels.—The aerodymamical laboratory at the Washington Havy Yard is operated by the Bureau of Construction and Repair for the Bureau of Aeronautics. Ml technical details connected with the tests and reports are under the direction and immediate supervision of Doctor A. l?. Zahm. The equipment consists of two wind tunneIsj one closed circuit type 8 by 8 feet in cross section at the testing plane, and one open circuit NT.P. L. type 4 by 4 feet in cross section. The larger tunneI is fitted with a speciaI six-component balance designed by Doctor Zahm and his assistants and constructed in the ‘Washington Navy Yard. As described in N. A. C?,A. Technical Report No. 146, this balance is equipped with automatic weighing beams which enable readings to be taken with great rapidity The smaller tunnel is equipped with a modified N, P. L. type of baIance, aIso having automatic weighing beams. The testing program is formulated for the greater part in the Bureau of Aeronautics and necessarily follows rather closely the design needs of the bureau. It is the policy, however, to make all tests as general as possible and to make available for general use all data which appear to justify publication. Such data are published from time to time as Technical Reports by the National Advisory Committee for Aeronautics, or, in special cases, by some scientific publication. Airfoils and wings,—A comparatively Iarge number of airfoils have been tested during the past year. The most important series of tests were those on the HandIey Page wing. This investigation, continued from 1922, represents a large amount of experimental work covering , detailed tests on five models. The second investigation in importance was the completion of a research on variable cambered airfoils, during which 12 models -were tested. A t.hhd investigation, on Iateral control, required a similar amount of testing. REPORT NATI02TAL ADVISORY COMXH7’EE FOR AEFLOFTATJTKIS. 21

In addition to the airfoil and wing investigation, a number of individual modeIs were tested from time to time. Among these -were two variable angle-variabIe c~mber modeIs supplied by inventors, 10 GWngen sections, 2 modified Sloane airfoils, and 13 other sections. Tests on the RAF-15 and Sloane models were carried to Iarge negative angks in order to secure design data for the upside down condition of flight. Tests were also made on the biplane wing arrangement used in the TS airplane, and on the monoplane wings used in the NW and CT airplanes. %wmI of the new airfoils appear to have unusualIy good characteristics and are to be given further tests. The best section in this class is the ~–9, a mod&ation of the CMtttingen No. 398. Another section of some promise is a thickened Sloane which has characteristics practically identical with the original section. AirpZanes.—During the past year 15 model airplanes have been given routine tests for Iift, drag, and moments under various conditions. The usurd routine test at the Washington hTavy yard is arranged to suppIy data on controI, stability and performance. In many cases, however, additional information, such as the resistance of some part or the effect of a motivation in the general arrangement, is also obtained. As an example, one model seapkme was tested with two types of tail surfaces, and another with five types of taiI surfaces, in order to obtain certain design data. Another model was tested to determine the effect of the shpstream caused by a modeI propeIler mounted in front of the engine housing and driven by an air turbine. It was formerly considered that wind tunnel test data was unreliable except for predicting stalling speed, contro~abfity, and bahnce. 130wever, the methods of correcting test data have recentIy been improved to the point where the complete performance maybe accurately predicted. Airplane par&.-A series of eight represent at.ive seaplane floats have been given thorough tests for air forces and moments, including the variation of drag with wind docit y. Two other seapkme floats and two boat seapkne hulk have been tested for lift and drag ordy. Tests have been made on two modeI bodies, one being for the TS seaphme and the other a modeI which w~s constructed during some shop experiments. It is proposed to exte~d these tests in the near future to include modeIs representative of current desigg. The proposed tests are to parallel the tests on seaplane floats and may be expected to supply ,vaIuable information for the deigger. Lighter-than~ir.—~eck tests have been made on two streamline modeIs supplied by the National PhysicaI Laboratory in connection with the “standardization” tests being carried out at various wind tunnels here and abroad. A model power car for the .ZR-l was tested to determine the eRect on the resistance of closing a visor hood. The data obtained checked vepy well with that calculated on the a~~~ption that the ~tefior eqosed parts ~o~d be subjected to a wind speed approximately proportional to the hood opening. A modeI of the A. P. kite balloon was tested in yaw to obtain data for comparison with other types, such as the ~, having radically different fln arrangements. The -relocity distribution around a modeI hull of the .ZR-l was obtained -from soundings in six transverse planes. The results, which have direct application in propeller desi=gn, are of interest in showing the nature of the airflow around a streamline body. Gcrwal.--+everal notabIe additions have been made in the equipment at the Washington ~avy yard. Automatic weig@g be- have been instalIed on the balance of the 4 by 4 foo~ tunnel and prove to be a great improvement. An automatic speed control has ilso been fitted to this tunnel with very satisfactory results. A very interesting manometer has recently been designed by Doctor Zahm. The tubes in this manometer are bent along the curv-e of a tractrix so that there is a constant precision in the reading at any speed. EUEEiUOFSTK!l!~~DS. Wind tunnel investigations.—The work in aerodynamics has been carried out in three wind tunnels, one 3 feet in dianmkr with a speed range of 11 to 180 miles per hour; one 4* feet in 22 REPORT NATIONAL ADVISORY COM?ZTICTEEFOR AERONAUTICS. diameter with a speed range of 17 to 90 miles per hour, and one 10 feet in diameter with a speed range of 15 to 70 miles per hour. Most of the work during the past year has been in cooperation with the engineering division of the Air Service, McCook Field, mar Department, Lhe Ordmmce Department, United States Army, and the National Advisory Committee for Aeronautics. A continuous program of testing and research has been carried on for the engineering division of the Air Service in connection with the design of the RS–I semirigid airship. Four proposed hull models were tested, measurements of drag, cross-wind force, torque, and cenkr of pressure being made. In conference, the aerodynamic characteristics were considered in connection with structural advantages and disadvantages and one of the hulls was selechxl. The pressure distribution over this hull was measured and the distribution of force computed for various attitudes of the model, ihe data serving as a partial basis for the keel design. Forces and moments on the hull were measured with 22 suggested designs of fins, the con lrol surfaces being in the neutral position, Damping coefficients were measured for the same surfaces on the Washington Navy Yard oscillator, which was loaned to the bureau Lhrough the courtesy of Doctor Zahm. Two of the besk designs were selected by the engineering division fur further tests with the control surfaces at angles. One of these designs was selected for use, and a study made of the pressure distribution over the after part of the hull with the fins in pIace. Measurements of the pressure over the fins are now & progress. At the beginning of the year, complete studies were made of the aerodynamictd characteristics of the military airship and the type A. P. high altitude observation balloon. In the field of bomb ballistics further measurements of the damping coefficients of bomb models have been made. An investigation of the validity of an empirical ruIe now used for the design of fin surface for bombs is in progress. The present rule relates hhe center of area of & meridian sec~ion of the bomb to the center of gravity. The correspondence between the center of area position and the center of pressure position is being studied experimentally. A comparison of tests on a 4-inch model in the 4&foot tunnel with tests of a full scale bomb in the 10-foot tunnel yielded very satisfactory results. Measurements in the high speed wind stream, obtained by discharging air from a compressor through an orifice, have been continued. Many of the measurements were made in cooperation with the Ordnance Department on projectile and bomb models, but during the past year spheres have been included. A balance has been constructed and is now being installed for measurements on airfoils of the same sections as those used in fihe high speed wind tunnel at McCook Field. Lift, drag, and center of pressure wil~ be measured. All of this work is made possible through the courtesy of the General Electric Co. The wodi on airfoik is in coopertition with the National Advisory Committee for Aeronautics. The determination of the speed of wind tunnel streams, independent of the use of the I?itot tube, has been contimed for the hTational Advisory Committee with certain refmemertts in the methods. No improvement in precision was obtained. The mean ratio of the speed determined by floating balloons to that determined by the Pitot tube is unity within 0.2 per cent, the mean deviation of about 40 determinations being of the order of 1 per cent. Studies of the steadiness of wind tunnel air streams have been made for the National Advisory Committee. The principaI result of the investigation is the demonstration of the existence of pressure waves of a frequency roughly equal to the natural frequency of station- ary sound waves in the tunnel. The importance of short large-diameter connections to the recording mechanism has also been shown, long connections producing resonance effects, small-diameter connections giving large damping. Aeromzni!ic insttmments section.—The outstanding feature of the work of the aeronautic instmments section of the Bureau of Standards during the past year has been the development of a variety of special instruments for use on the United States Navy rigid airship S.hnan- CJOU7J.The importance of having accurate instruments to aid in the navigation of this ship has been appreciated by those responsible for its construction and operation, and this has brought about the adoption of a comprehensive program of instrument development at the Bureau of Standards by the Navy Department. Among the instruments which have already REPORT NATIONAL ADTTSORY COMMITTEE FOR AERONAUTTC33. 23

been comp~eted for the Slwnandoah are a temperature-compensated altimeter, a sensitive landing altimeter, g r~te-of-climb indicator, and electric turn meter, two suspended head electric airspeed meters, an electric thermometer and a fabric tension meter. In addition, the usual program of research and development work on aeronautic instruments has been continued in cooperation tith the hT~ticmal .Advisory Committee for .leronau- tics, the Arm-y and hTavy Air Services, and other Government departments. A considerable amount of routbe testing has also been done. The investigation of all types of instrument cliaphra=as for the National Advisory Com- mittee for Aeronautics has been eont.inued. Reports on several phases of this work have been brough~ nearI-y to completion. The theory of the deflection of slack diaphragms has been formulated and has been v-eritled experimentally in numerous wideIy different cases with an accuracy of 5 per cent or less. It is no-w possible by using this theory to desibm slack diaphragm pressure elements to meet specified conditions and to give almost any desired load-deflection — curve. The drift and recovery curves obtained from the tension tests referred to in Iast. year’s . report h~ve been investigated in the light of Boltzmann’s theory of elastic time effects. With this theory it has been found possible to predict the reco-rery curves, once an ~xpression has been found which fits the drift cur-res accurately. Using the expression representing the drift, it is possible to predict the time hysteresis. Making use of the drifh curves obtained from tests of Bourdon tubes to compute the time hysteresis curves, then comparing these with the rxxperimenta.lly determined hysteresis curves, it has been found that. the time hysteresis comprises approximately half of the total hysteresis loop, directional hysteresis (i. e., the German “ elastische hysteresis”) accounting for the remainder. By subtracting the time hysteresis from the total hysteresis it has been possible, therefore, to determine the shape and ma=titmde of the directional hysteresis loop. A new theory of the deflection of Bourdon tubes has been developed and has been tested experimentally. This theory has been found to agree -with experimental results much more olosely than any of the theories previously formulated. A report on aerial riavigation and one on night and cIoud fl-ying have been prepared and are nearIy ready for publication.

>LW%CETWET’TS INSTIIW1’E OF TECHNOLOGY. Equiprnen~.—The mosti notable addition to the equipment of the. aeronautical laboratory during the past year is the large wind tunnel, 7~ feet in diameter, which is now in fti opera- — tion. As the mmdtt of the suppression of all honeycombs in the throat of the tunnel, the only straightening device being placed well out toward the mouth of the entrance cone, the efficiency proved somewhat higher than had been anticipated, a wind speed of 90 miles an hour being attained with an e.xpediture of 125 horsepower. The flow is satisfactorily steady, the wind speed being kept ~ery closely at any desired value by an automatic regulator, similar to that aheady in use on the small tunnel bufi with tthe addition of a magnetic vibrator to keep the regulator arm oscillating continuously and to count eraci any time lag and rew.dtant tendency to “hunt” which might arise from the large inertia of the armatures of the electrical machinw on which the regulation uRim&teI-y acts.. The turbulence in the new tunnel seems fio be acep- tionally low, presumably because of the distance bekween the honeycomb and the model and the change of diameter between the tmo, and the effect of Io-iv turbulence is, as usuaI, to decrease —— the m~~imum lift of airfoik. The maximum lifts recorded for typical sections are somewhat less than those found for the same sections by most other American tunnels, but somewhat more than have been recorded at GotLingen. The balance used supports the model in the tunnel only by wires. The drag is taken through a 45° Ii&age, as at Gottingen, but the points of tittaclmnent of the ties are not the same as those used at Gottingen, and the baIance itself is quite different from the German design in mechanical detail As two sets of drag wires are used, with independent attaebment to the balance, yawing and rolling moments, as -weL1as lift, drag, and pitching moments, can be measured, all five reading~ being taken without disturbing the model or readjusting the balance. ?3—2+3 24 WPORT NATION-M ADVISORY COM-MITTEE FOR AERONAUTICS.

Wind twnnel$ow investigations. —In addition to the usual routine studies of the flow in the large turmelj incIuding the making of transverses, the use of recording airspeed and yaw meters, etc., a detailed investigation of the effect of turbulence has been undertaken. Measurc- rnents of the lift and drag of several airfoiIs, as well as of the drag of a number of other objects, have been made in the small tunnel with screens of various degrees of closenms of mesh placed across the stream in front of the modeI, and the indication has been that the scale of the dis- turbarices which constitute turbulence is at least as important a factor as the total extent of the disturbance. The larger the mesh of the screen, within the Iimits to which the experiments were carried, the larger was the effect on aerodynamic forces. Airfoil tests.-The testing of airfoils has beeri carried on in both wind tunnek, about 30 sections having been tried in all. For the purpose of providing airpIane designers with data which would certainly be directly comparable a series of standard tests have been undertaken, about 20 sections having been selected from among the best produced in any of the laboratories of the worId. Models of these sections have been made up in a uniform size of 36 by 6 inches on the Nichols wing machine and have been tested at uniform speed of 40 miIes an hour, A similar series of tests is later to be made at higher speeds. The sections tested up to the present time include nine of American, one of British, one of French, and four of German origin. Airpkze model tests.—The practice of making an extended series of wind tunnel tests on Uhene< airplanes designed for the Army Air Service has continued, and about a dozen complete models have been tested during the year. Very interesting conc~usions with regard to do-ivn- wash and its effect on the balance of the airplane, as well as to the way in which balance depends on the aspect ratio of the tail, have been arrived at, and further light has been gained on the difference between real and ‘[ apparent” or “calculated” dowrnvash and on the factors which control the relation between those quantities. Control.—The investigation of controllability and maneuverability characteristics hw been continued, and the completion of the rolling and yawing moment balances ha~e made it possible to add a study of aileron behavior to the work previo~ly done in determining the effectiveness of the elevator and rudder on each model tested. The most important general conclusion has been that an aiIeron on the lower wing of a biplane is superior to one on the upper wing from every point of view. lt further appears that the action of the ailerons depends very largely on the section of the wing to which they are attached, and that it is unsafe to consider the resuIts of model tests made with a single section as of generaI application. The prediction of maneuverability characteristics from wind tunneI tests is still being studied, and a theoretical minimum turning radius is now calculated for alI models. Only the resuIts of an elevator control test are needed to make this prediction if a vertical bank is assumed. .Miscellaneows.-A number of short researches, not falling directly in any of the classes enumerated above, have been carried to completion, Among the most interesting were a determination of the effect on airfoil performance of corrugations and striations of various forms on the surfaces, and % series of experiments on the pressures arising from the impact when a flat or curved surface, corresponding to the bottom of a seapIane float, is suddenIy dropped onto smooth water.

REPORT OF COMMITTEE ON POWER PLANTS FOR AIRCRAFT. ORGANIZATION. The committee on power pIants for aircraft is at present composed of the following members: Dr. S, W. Stratton, Massachusetts Institute of Technology, ch%irman. Henry M, Crane, Society of Automotive Engineers. Harvey N. Davisj Harvard University. Dr. H’. C. Dickinson, Bureau of Standards. Leigh M. Griffith, Langley MemoriaJ Aeronautical Laboratory, ●

REPORT 27ATIONA.iLADvIsORY COMMITTEE FOR AERONAUTICS. 25

W. S. James, Bureau of Standards. Edward T. Jones, engineer@ dhision, Army Air Service. Lieut. Commander B. G. Leighton, United States Navy. George W. Lewis, National Advisory Cornrdtee for Aeronautics, vice chairman. Flmo-rIoNs. The functions of the committee on power plants for aircraft. are as follows: 1. To determine which problems in the field of aercmautic power-plant research are the most important for investigation by gowmunenta.I and private agencies. 2. To coordinate by counseI and suggestion the research work invo~ved in the invest iga- tion of such problems. 3. TO act as a medium for the interch~~e of information regarding aeronautic power- p~ant research in progress or proposed. 4. To direci and conduct research on aeronautic power-pIant problems in such laboratories as may be pIaced either in whole or in part under its direction. 5. To meet from time to time on cdl of the chairman and report its actions and recommendations to the executive committee. By reason of the representation of the Army, the Nawl the’ Bureau of Standmds, and the industry upon this subcommittee, ib is possibIe to maintain close contactt with the research work being carried on in this country and to exert an influence toward the expenditure of energy on those problems whose soIution appears to be of the greatest importance, as well as to a-roid waste of efforb due to unnecessary dupEcation of research. The cow-t tee on power plants for aircraft has direct contrvI of the power phmts research conducted at Lar@ey Field and also of speciaI investigations authorized by the committee and conducted at the Bureau of Standards. Other power-pIant investigations undertaken by the Army Air Service of the Bureau of Aeronautics are reported upon ati the meetings of the committee of power plants far aircraft.

LANGLEY >lEllOELhLAERO?L4U~C.AL JL4BOEATORY.

lliel injection engine—+pray @.otoqrapiiy.-The fuel injection spray photography research was prosecuted according to the plan presented in the report for last year, the development being carried on at the request of the Bureau of Aeronautics, Navy. The difticuhy of obt aining prompt deliwry of the special appar~tm required and the necessity of designing and building in our own shops such apparatus as could not be obtained to advantage from commercial estab- lishments, has caused frequentt and extended delays. These delays together with the pressure of other work and the lack of persomel have com~iderably retarded the prosecution of this work. The original scheme of the apparatus has been changed considerably in order ihat light flashes of the desired intensity and frequency n@ht be obtained. The electrical relief wdve method of controlling the frequency of the light flashes, using a water resiskauce as described in the report for 1922, did not produce the exact results desired, because the large current required in producing the proper illumination ab the spark gap caused a prohibiti~e energy loss. The water resistance has been replaced by several inductance coiIs and a special synchronous interrupter switch, placed in series with the spark gap. In this case the valvular action is produced by the large inductance of the coils preventing sudden changes in current flow. While this system is somewhai more complicated, it is, nevertheless, very much more efficient. The dark fieId method of spray illumination -was retained. The spark gap was Iocat-ed at one focus of an elliptical mirror and the spray chamber was arranged to take the indirect light at a point sfight.ly beyond the other fecus. The electrical discharge across the gap caused a deposit to be formed on ~he mirror which became so corroded as ho be umafiisfactory. The necessity of &ding a suitable remedy for this action and the difficulty of obtaining a good mirror surface led to the trial of a system empIoying a parabofic mirror to reflect the ~~ht from the gap in parallel rays through the spray chamber, placed at an angle with the light beam. This system produced an even illumination which can be increased to the desired amount by 26 REPORT NATIONAL ADVISORY COMMITTEE FOR AEROiVAUTICS.

the addition of more reflectors. It is expected that satisfactory photogmphs will be obtained with this arrangement without very much difficulty. Fuel churacteri&x.-A research has been undertaken to determine the vapor pressures of various fuels and liquids zt high temperatures. It is hoped that information will be obt~inod -which will assist mat erially in the solution of the fuel injection engine problem. Little work ‘ has been done on this subject heretofore, wzter being the only liquid for which t,his rel%tion seems to have been defini~ely established at temperatures pertaining to the fuel inj cction engine, Consequently the vapor pressure of water was determined first in order to connect tho present work with that done previously. This is being followed by determinations up[on aIcohol, benzo], Diesel fuel oils, gasoline, and kerosene. Another phase of the general research is directed to the determination of the coeffkien~a of discharge for orifices suitable for use in injection nozzles. Orifices of 0.004 inch to 0.025 inch diameter and of various lengths are being used. Diesel fuel oil has been tested exc.lusivcly thus fm ‘but these tiests will be followed by others using such other liquids as are of pertineni int crest. Injection valves and pumps.—The study of fuel injection engine fuel pumps and injection valves has been continued in the laboratory both on actual engines and on the bench. The cam-operated, spring-loaded pump constructed for the preliminary work with the single cylinder Liberty has been refined in design and another pump constructed which is more comp&cL , and stronger than the original one. A pump employing sleeves around the plunger for timing the starting and ending of injection was constructed and a more elaborate design of ~he same general type has been studied on the drawing board. A large number of designs using the pump suction valve as a means of timing the injection have been studied and the most promising of these designs is being constructed and will be subjected to bench and engine tests, The relative merits of both packed and lapped plungers have been studied, as a result of which this pump is to be first constructed with a packed plunger, although provision is made for the sub- stitution of a lapped plunger construction. The pump plunger and suction valve control will be operated by an eccentric and the rod connecting the eccentric to the valve control will act against adjustable cam biocks so that the injection may be timed to occur at vmious portions of the plunger stroke, thus taking advantage of the velocity change of the pIunger to obtain different rates of fuel discharge, A compIete study was made of the deflection of solid and orfice diaphragms with both concentrated and distributed load, using small single and multiple diaphragms of various thicknesses and of sizes suitabIe for use in injection valves. A number of injection valves employing different combinations and arrangements of these diaphragms have been studied and several of the more promising have been constructed a~d subjected to laboratory test. Excellent atomization is obtained with this type and sufficient experience has been secured to permit rationaI design to meet specified conditions, Apparatus is being constructed which m.ii enable the characteristics of a given injecLion system, consisting of fuel pump, injection valve and connecting tube, to be more carefully and more completely studied. The pump will be driven by an adjustable speed motor be~ted to the jack sha.ft upon which the pump is mounted. A large disk also mounted on the jack shaft and rotating with it will provide for the determination of the timing of the ~ctual discharge in relation to the pump setting, and of the distribution of the quantity discharged over the period of injection. Consequently, the effect of changes in the setting and construction of the pumps and valves, and the effect of changes of size and length of the connecting tube, may be rationally evaluated. E@ne test wo~k.—The study of fuel injection engtie problems with the single cylinder engines has been continued throughout the year. The limi~ations of the Liberty engine cylinder as adapted for direct fuel injection and compression ignition have been approximately determined. At the same time information has been obtained that will guide the improvement of that performance by design modifications. Tests were made -with both external and internal injection, combined with spark ignition, using a number of pistons giving various ratios of REPORT NATIONAL ADVISORY COkXITTEE “FOR AERONAUTICS. 27 compression and fuels consisting of different proportions of gasoline and b enzol. This work enabled a direct comparison to be made with the carburetion engine ae regards capacity and fuel economy, and with the compression ignition engine as regards capacity. Using compression iggtio~ and a compression ratio of 11, an L M. E. P. of 119 pounds has been obtained at 1,800 r, p. m. with Diesel fuel oil containing 3 per cent of tetraethyl lead. With spark iatit.ion, internal injection, and a compression ratio of 5.4: an I. M. E. P. of 13s pounds was obtained zt 1,735 r. p. m. with a 25/75 benzol-aviation gasoline mixture, vrhiIe with spark ignition, external injection, and the same compression ratio, an I. M. E. P. of 148 pounds was obtained XL 1,750 r. p.m. and an L 3L E. P. of 150 pounds at 1,900 r. p. m. using a 50/50 benzoI-aviation gasoline mdw.re. Thus it is seen that with internal injection and spark ignition results compara.bIe to Liberty 12 cylinder practice are obtained, bui khat external injection and spark ignition yield appreciably greater power. The power with compression ignition has so far been Iess than with any of the other arrangements. These tests, however, can not of themselves be taken as conclusi~e for all compression ignition work, since the form of the Liberty cylinder is very poor for such a high Compression ratio and infiernd injection. A cylinder barreI arranged for detachable heads, together with two types of cylinder heads to fib, have been constructed for use in connection with single cyIinder test work. The combustion chamber forms of these heads are more fa-ror- abIe for 8 number of types of fueI sprays. A Liberty cylinder has been modified for the study of two cycle fuel injection electric iatition operation by cutt~~ ports in the bottom of the cyLinder and adding suitable scaveriatig %ir ducts, chqjng the water jacketing, and by providtig special cam shafts to operate both the inlet and exhausfi valves as exhaust valves. In this application a separate bIower forces scawmggg air thro~~h the cylinder ports and out the exhausti mdws, driving the exhaust gases before it. The work to date has been with pistons giv& 5.4 and 5 compression ratios and . 115 pounds 1. M. E. P. obtained. With the present apparatus it is expected to approximately determine the air pressure necessary to secure satisfactory scavengtig and, in a general way, &helimitations of two cycle application. The universaI single cylinder test engine mentioned in the reporfi of last year mm set up in the labomt ory for dynamometer operation and was sub ject-ed to a series of calibration tests. Considerable delay was experienced due to the difficulty of obtaining satisfactory cylinder head castings. Several modi&atione in the rather compIicat-ed valve operating mechanism have been necessary, but the functions of -w_riabIe compression, variabIe valve Iift, and variabIe valve ope@~ and closing have thus far been satisfactory. This engine has been operated as a carburetion engine to date, but it is pknned to change LOfuel injection as soon as the required pump and injection nozziie are a~aiIabIe. Supercharging corapressor—l?oots type.—The problem of the Roots type compressor for supercharging aircraft en=ties has been continuously studied thro~ohout the -year. Ffigh~ t-este in the modified D13-4 viere continued with the origimd supercharger until its performance t.o 20,000 feet was establkhed. It has been possible to repeatedy climb to an aneroid altitude . of 20,000 feet in 20 minutes- The best climb of this same airpIane with pIai.n engine wae 12,000 — feek in 20 minutes, or to a ceiling of 14,500 feet in 36 mimutes. The standard radiator installation pro-red inadequate for the increased quantiby of heat to be dissipated when full supercharging was a.ppLied, so that it wae necessary to provide an auxiliary radiator. Thie undoubtedly affected the performance of the airplane advemely. Lack of suitabIe oxygen equipment prevented flights to higher altitudes at that time. FolIowirg the above series of flight tests, the or@al supercharger was modified by changing the ratio of impelIer to engine speeds from 1.5 to 1.94, thus obt ~in@ greater supercharger capacity md consequently better engine performance at the higher altitudes. FIight tests of the motied supercharger showed that the time of climb to 20,000 feet was somewhat greater than with the original gear ratio. It has been possible, howe~er, to maintain ground level pressure at the carburet-er to slightly over 20,000 feet, as compared with 13,000 feet with the 28 REPORT TNATIOIJALADVISORY COMMITTEE FOR AERONAUTIC%,

1.5 gear ratio. Oxygen equipment was instaIled and flights approaching the absolute ceiling were made, &tta.ining an aneroid altitude of approximately 30,000 feet. At the time the gear ratio was increased impellers made of magnesium alloy were substi- tuted for those of aluminum alIoy previously used. In the Iabol story tests made bcfom the installation of the modified supercharger in the airpIane this metaI proved to be better than the aluminum alIoy, especially as regards the manner in which it withstood contacting between the impellers. The aIuminum aIIoy impelIers tended to abrade or gall badly upon contacting, whereas the magnesium alloy surface hardened at the point of conttwt and thus increased its abi~ity to withstand, further contacting. Another Roots type supercharger of the same dosign was constructed and installed in ~ DT-2 airplane with a Liberty engine at the request of the Bureau of Aeronautics of the Navy Department. This supercharger proper is of the same capacity and design as the original, although some minor design changes were made in the connections. The air-duct sys~em connecting the supercharger and carburetors was modified somewhat in order to provide gmator adaptability to temporary aIterat,ions to determine the optimum air-duct arrangement. Flights to 20,000 feet have been made, but difllculties with det~iIs and accessories have prevented any very conclusive data from being obtained to date, Numerous design details have been made for an improved Roots typo supercharger, based upon experience with the original supercharger. It is hoped to complete and test u sample of ibis improved design during the coming year. Further study hw also been mfide of t]~o general problem of supercharging aircraft engines and of the difierm Ii Lypes of compressors that may be used for this work. Otler supercharging proHems.—A research to determine the adaptabili~y of air-cooled engines to supercharging has been undertaken at the request of the Bureau of Aeronautics. Construction of special apparatus has been started and plans have been practically completed for initiating the actual test work. It is plmmed to use a.Lawrance J-1 engine instdcd in a TS airphme, mzking a temporary instaIlatiou of one of the present oversize superchargers in ordor to quickly obtain some information as to the limit imposed on air cooling. The high-speed fan type compressor mentioned in the report for 1922 has had ahnos~ no attention, owing to lack of personnel and the desirability of concentratkg on the bypo of supercharger of greatest immediate promise. The fan type has been studied to some extent, however, m d a promising form of very light rotor constructed. As soon as possiMe it will Im set up in the laboratory and dynamometer tests will be made to determine its characteristics. The rotor design employed is quite a departure from usual commercial practice and seems to have considerable promise. Power plant laboratory equipment.—A new 100 h. p. electric dynamometer has been installed m the second unit of ‘the power-plant laboratory and will be used primarily for fuel inj oc ticm engine research. A number of changes have been made in the 75 h. p. dynamometer ‘and an exhaust disposal system is being installed to connect that- machine wi~h the sysk.rn on the 400 h. p. dynamometer in the same building. . Much time has been spent in the periodic overhaul of the two gasoline engine driven electric generating sots used for the operation of tihe dpamometers. This has involved a considerable expense and the frequent failure of these units has caused the loss of many tests. Ib is hoped to repIace them with a 100 h. p. motor-generator set drawing from the service power lines. The instrument work in connection with the power-plant research is dcsoribed in the report of the committee on aerodynamics. BUREAU OF STANDARDS. The aeronautic power-plant work at the Bureau of Standards during 1922 and 1923 has been carried on in cooperation with the IITationaI Advisory Committee for Aeronfiuticsj the Bureau of Aeronautics of the Navy Department, and the engineering division of the Air Service. Aircraff-engine perfornmnce.-Reports have been submitted Lo the Bureau of Aeronaut ics covering very complete performance tests of two aircraft. ergines, the P&ckard 1551 and the REPORT NATIONAL ADVISORY COMMITI’EE FOR AERONAUTICS. 29

Wright H-3. These engines had been subjected to a program of altitude. chamber tesis of broad scope. The Bureau of Aeronautics has requested that other en=ties be given similar bests during the coming year, For several years the relation between the power deveIoped by an engine and the intake- air temperature has been under investigation. This work has been supported by the Air Serv- ‘ ice and the National Advisory Cwnmittee for Aeronautics and a reporb has been submitted to the h=dter for publication. A report on the effect of changes in compression ratio upon en=gine performance is now in . preparation. This subjeci also has been under investigation for severaI years. A report entitled “The Relation of Fuel-Air Ratio to En=gine Performance” has been prepared for publication by the Na~iomd Advisory Committee for A.eromutics. This report is based on an analysis of a very Iarge number of engine tests and contains information of material value to engine designers and users. lgnit~on.—The relation between character of the ignition spark and flame velocity has been imm.stigated for several explosive gas mixtures, inckling those of gasoline vapor and ~ir. - YeIocities have been measured by firing a quantity of gas inclosed in a soap bubble or in a thin-walled glasw buIb and recording the flame spread photographically. For this work the dedopment of much special apparatus has been necessary. This, together with the results obtained, is described in a report entitled “Effect of Spark Characteristics of Flame Velocity,’) which has been prepared for publication by the hTational Advisory Committee for Aeronautics. Spark gaps are used extensively in kst~~ ignition apparatus, and at the request. of the Air Service the behavior of various spark gaps has been inwstiigated with a view to standard- izing the type which should prove to be most suitable for such testing work. The dificulty of obtaining regular spark@ voIt.age was found to be greater than had been anticipated and although much valuable information on the characteristics of spark gaps has been obtained an entirely satisfactory form of gap has nob been developed. A comparative study of 10 radically diRerent types of ma=guetos and spark coils has been pursued, with the object of obtaining more definite knowdedge of the electrical phenomena involved in the function@ of an ignition system and their relation to desi=n. Tests are being made to instigate various empirical and theoretical relations bet$een the voltage developed and the conditions of speed> current, etc., under which the system oper%tes. Such know-ledge should permit drafting suitabIe specifications and methods of te+ for ignition systems and should assist manufacturers in improving their product. Carbureticm.—Under authorization from the Bureau of Aeronautics of the N-avy Depart- ment a rather complete investigation has been made of the characteristics of two types of carburetors as mounted on a Lawrance engine. For this investigation the engine was installed in the altitude chamber and fuel-air measurernertt-s made under conditions @picaI of those encountered in service. A report of this work is being prepared for the Bureau of Aeronautics. In conjunction with the altitude chamber tests of the Packar7i 1551 and the Wright H-3 [email protected],special tests of five carburetors were made. The performance of these mrburetor~ is discussed in the reports of these en=gine tests which have been submitted to the Bureau of Aeronautic. A report of an investigation of se-wm.l carburetors with regard to the relation bet-iveen their meter@ characteristics under steady and pulsating air fIow has been submitted to the engineering division of the Air Service. The investigation of the factors controlling the formation of liquid drops from jets issuing from orifices of ~arious t~ee and the -transportation of such drops in air streams has been continued. Fuel.s.-SpeciaI fueIs for aircraft engines, chieff y benzol-gasoline and alcohol-gasoLine blends have been investigated under authorization from the Bureau of Aeronautics of the hTavy Department in paralIel with a general investigation of fuels for high-compression en=ties authorized by the ATational Advisory Committee for Aeronautics. As a part of this investigation an engine having a compression ratio of 14 to 1 has been operated satisfactorily. This 30 REPORT NATIONAL AD}71SORYCOMMITTEE FOF\AEROI$AUTWS, ratio is believed to be higher than any previously employed in an internal-combustion engine operating on the Otto cycle. Some of tihe outstanding results of these tests were presented at the January, 1923, meeting of the Society of Automotive Engi~eers. Physical arid chemical characteristics of fuels have been studied with specird refemmcc to the separation temperatures of l.dended fuels and the relative tendencies of the various fuels to cause corrosion. Progress reports covering the above work have been submitted to tho Bureau of Aeronauticsj and a report summarizing the work done to date is.in preparation for publieztion by the hT~tional Advisory Committee for Aeronautics. A method hm been developed for measuring the minimum temperature at which the fuel in a mixture of fuel and air wiIl remain in the vapor state, This method has been applied to a number of gasolines and a report of the results of this work is in preparation. [nternal-comk.stioia engine luZwication.—The major portion of the lubrication work specifically reIating to internal-combustion engine problems has been requested and suppor~ed by the engineering division of the Air Service. One of the problems most actively investigated has been that of developing a mot.hod for the determination of the relative resistance of oiIs to partial oxidation similar to th~~ proposed by Waters but more suitabIe for routine tests, Maay methods have been investigated and it is confidently expected that a satisfactory method will be developed during the ensuing year. Engine tests have been carried on throughout the year with the Lwofold purpose of (1) ascertain@~ the conditions of engine operation which are of primary importance in controlling the formation of solids in the combustion chambers and crank cases of engines, and (i!) selecting the program of tests most suitable for a comparative study of oils with reference to their tendencies Lo form solids in combustion chambers and crank ca~es of engines. QuaIit ative information as to the effect of the temperature of a metal surface upon the rate at which “ carbon” is formed upon it has been obtahed and made avaiIable to automoti~e engineers throngh the trade press. The operation of the specially designed apparatus for the investigation of journaI bearing lubrication has been materiality improved and satisfactory readings considerably below the region of the minimum coefficient of friction have been obtained. Apptiratus has been designed and constructed both for measuring the pIas6icity of oils at low temperatures and for investigatirqg the sigtilcance of the pour test in estimating the relative ease with which oiIs will be drawn into aircraft enggne oil pLunps under winter conditions, Cooling probZems.—For the past three years, an investigation under the title “Ballast Re- covery for Airships” has been in progress. At the request of the Air Service this work has been considered conticientlal up to the present time and hence has not. been me~tioned in pra- vious reports. The ori@zI request of the Army Air Service was for an investigation of the possibilities of compensating fm the loss in load, due to the fuel consumed, by the condensation of the waher vapor in the engine exhaust. A study of the problem indicated it to be femiblo . and subsequently two water condensing units, each for a 300-horsepower engine, were designed and constructed. To date, one of these units has been given a 50-hour ground test and tho other a 100-hour tat and a flighk test of 25 hours. The performance of both units has been so satisfactory as to demonstrate beyond any doubt that ample ballast for the purposo desired can be recovered with an apparatus of practicable weight. A complete report ent.itIed “ His- tory, Design, and Theory Relating to Ballast Recovery Project” has been submitked to the ~gineer@ division of the & Service. .kn investigation of the air flow through radiators mounted in other than free air streams has been conducted under authorization from the National Advisory (!ommittee for Aeronautics. The air flow measurements have been made in flight, the flight work being made possibIe by the cooperation of the fiy~m personne~ of the Bureau of Aeronautics of the Navy Department,, Information &rived from this investigation should greatly increzse the value of the published results of the bureau)s comprehensive laboratory tests of the characteristics of aircraft radia- REPORT NATIONAL ADVISORY COMXITTEE FOR AEROISAUTIU3. 31 tors by making possible their application to problems invoIv@ radiatas mounted in other than free air streams. At the request of the NationaI Advisory Committee for Aeronautics the xork on aircraft radiator characteristics is be@ extended to higher air speeds. With the wind tunneI equipment now available at the bureau it will be possibIe to obtain measurements at an air speed of 150 miks per hour. It is believed possibIe to complete this investigation during the coming -year. A critical study of the behavior of Pitot tubes as used to measure air flow through the — celk of aircraft radiators has also been undertaken at the requast of the NationaI Advisory Commiktee for Aero~autics. The probkm has been investigated from both theoretical and experimental standpoints with concordant results and a reporb of the work is being prepared. Phenomena of combustion.—This work, which has for itis chief aim an investigation of the kinetics of expIosive gaseous reactions, has been supported as in pretious years by the National Advisory Committee for Aeronautics. A description of the device and method developed for this investigation has been submitted to that committee for publication. This device makes it possibIe to determine not only the rate of flame movemen~ in space, buh also the rate of flame penetration relative t.o the reacting gases. Since the device permits the reaction to run its course at constant pressure, and since the mixture ratio of the gases may be expressed in terms of concentration (partial pressure), it becomes possibIe to express the relation between the@O of flame penetration (reaction rate) and concentration. In this way the interesting reIation has been revealed that the rate of flame mo-rement reIative to the mixture is proportional to the product of the concentrations of the reacting components. The effect of inerb gases on the reaction rate k also indicated by the above relation and has been satisfactorily checked by many measurements. The method also per~ts the determination, from the observed velocities, of the number of molecules taking part in the reaction in much the same way that this important fact is revealed in ordinary fiameless reactions. This indication shouId prove useful in dealing with fuels of indeilnite composi~ion. The efIecb of presmre upon concentration and hence upon reaction rate should be a function of the molecular number of the reaction. This important relation has never been quali- tatively investigated over the r~we of conditions met with in engine practice. Provision has been made and apparatus devised for a thorough study of the effect of this factor on frame velocity. ?iEwENGINETYPES.

The new types of engines under de-re~opment by both the Bureau of Aeronautics of the lNavy Department and the enggeer~w ditiion of the Army Air Servicex and described in the. eighth annual report, have been completed during the past year, and many of the ergines —. ha~e undergone preliminary tests. One of the outstanding results of the past year’s work -was the decision of the Bureau of . Aeronautics, Navy, to abandon de fiitely the use, in future naval aircraf~ construction, of water-cooled engines of less than 300 H. P. The development of direc~ air-cooled engines, and particularly of the Lawrance model J–ll 200 E. P. en=tie, has progressed rapidly during ~he past year, and engines of this t.~e are taking their place in service. Development of the direct air-cooled engine to a point where in dependability and in .— all-round serviceability y it compares favorably with the more commonly used water-cooled types, is an accomplishment of the greatest importance to aircraft operations, because it permits the complete elimination of the weight and complication entailed in the water, radiator piping, fittings, and accessories requmed in the cooling system of the water-cooIed engiue. The we&ht of the COO%V system of the water-cooled engine is usually in excess of 25 per cent of the weight of the engine itself. .ln air-cooled engine development for the Xavy is being carried on by the Kinney Manu- facturing Co., who are producing a 60 H. P. five-cylinder radiaI engge. %@e-cylinder tests of this emgtie hare been completed, and the first en.gge is being assembIed and will be tested before the end of the present year. 32 REPORT 17ATION’ALADV180RY COMMWT%E FOR AERONAUTICS.

A large number of Wright (Lawrance) J-1, 200 H. P. air-cooled engines have been in flight service and have definitely proved their serviceability. A rmmber of defects have been uncovered and a new model known as the Wright J-3 is being produced. This engine has incorporated in it the modifications found necessary as a remdt of the block and flight testing. The first of these engines is expected prior to the end of the present year. A nine-cylinder 6 by 6+ radial e@ne known M the ruodeI P-1 is being developed for the Bureau of Aeronautics of the Navy by the Wright Aeronautical Corporation. This engine is raked at 400 h. p. and 1,650 r. p. m. A Iarge number of singIe-cylinder tests have been conducted, and it is hoped that the first experimentally compIete engine will be avaiIabIe for test during the early part of 1924. The Eng”meering Division of the Army Air Service has developed two very successful air- cooled cylinders, the first of which is known as type K. The design was primarily intended for engines of 200 h. p., and can be adapted to a Lawrence J–1 engine. A similar cylinder dmign, known as type J cylinder, has been developed for engines developing 400 h. p., and can be adapted to the Wright radial nine-cylinder air-cooled engine. The Army Air Service has been concerned chiefly with the final development of the ‘W 700 h. p. engine, and the co,ntinuatiort of the development of the Almen barreI-type engine in col- labo ation with Almen Motors (Inc.). The new model of the ALmen engine has been received, i is now being tested, and shows great promise. The weight per horsepower compares favorably with the best type of water-cooled engine now in service. The supercharger development at McCook Field has brought out the side-type turbine supercharger, which has made possible a much cleaner installation, reducing the head resistance and eliminating the heating d.ifficuIties. The development of the turbine-type supercharger with a gear drive is also under way. Last year the Bureau of Aeronautics adopted test specifications requiring 300 hours’ full- throttle operation as a goal to be obtained in engine durability. The Aeromarine U 8 D, the Wright model E-4, the Packard model 1551, the Curtiss model D-12, and the Lawrence model J–1 epgines were subjected to these tests, and as a result many inherent wealmesses were dis- covered and steps taken to remedy them. The special cylinder blocks and valve gear designed for the Liberty engine ha~e bmn tested and the parts released for production. The Aeromarine Plane & Motor Co. will complete a number of these cylinder blocks during the current year. The use of these cylinder blocks has increased the power and economy of the Liberty engine materially above that of the original machine, The Packard model 1300, 12-cyIinder, 375 h. p. engine, has successfully completed the 50- hour acceptance test. Several engines of this type are being produced and wilI be placed in flight service. The characteristics of this engine are extreme compactness and low weight per horsepower. “The Curtiss model D-12, 375 h. p. engine has been equipped with oversized cylinders and high compression ratio pistons and operated at high rotative speed. Under these conditions the engine has developed 500 h. p. at 2,300 r. p. m. When the excessive power outpui of Lhis engine is considered, the durability obtained is to be commended. Several engines of this type have been purchased and have completed a number of hours’ running, both on the test stand and in the air. ,The Bureau of Aeronautics has pIaced approximately 40 Wright model T-2 engines in service. This engine has shown exceptional durability and is very satisf actory, one installation in a DT airpIane operating for a period of approximately 250 hours. Tests are under way with T–2 engines varyhg the compression ratio from 5.5 to 7.1. At a compression ratio of 7.1 ~he engine has developed 780 h. p. at 2,250 r. p. m. A design of a Wright modeI T–2 engine has been completed providing for the use of reduction gears. Thg reduction gems have been compIeted and have successfully passed preliminary tests and are awaiting installation in the engine. The Aerornarine Plane& Motor Co. is developing for the Bureau of Aeronautics a 12-cylinder engine of unique design. The design is such as to permit of a very short engine base and crank REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. 33 shaft. Sin@-cyIinder tests have been c,ompIefied and the engine is being assembled. lti is expec~ed thafi the first engine will be ready for tmsfiwithin two or. three months. The engine is rated at 620 h. p. at 1,650 r. p. m., and will w<~h about 1.7 pounds per horsepower. The over all dimensions are approximately the same as the dimensiom of the Wright model H–3.

REPORT OF C!OMXITTEE ON XtATERIALS FOR .4JRCRATT.

Prof. Charles F. Marvin served as chairman of the committee during the period covered by this report. He -was succeeded by Dr. George II. Burgess on October 18, 1923. Follo-ivirg is a statement of the organization and functions of the committee on materials for aircraft: O?lGkliTIOX.

Dr. G. K. Burgess, Bureau of Standards, chairman. W. S. K. C!oIby, American Manqesium Corporation. Mr. 13enry A. Gardner, Institute of Industrial Research. Prof. George B. Haven, Massachusetts Institute of ‘l?echuology. Commander J. C. Hunsaker, United St at.es Navy. Mr. Zay Jeffries, Aluminum Company of America. Mr. J. B. Johnson, engineering divkion, Air Service. Prof. E. P. Warner, Massachusetts Institute of Technology, Dr. CarIile P. Window, Forest Service. Prof. H. L. Whittemore, Bureau of Standards, acting chairman. FUNCTIONS.

1. To aid in determiningg the probIems reIatiug to materials for Sircraft to be experi- rne~t ally attacked by governmental and private agencies. 2. To endeavor to coordinate, by counsel and suggestion, the research and experimental work involved in the investigation of such problems. 3. To act as a medium for the interchange of information regarding investigations of materials for aircraft., in progress or proposed. 4. The committee may direct and conduct research and experiment on materials for aircraft in such laboratory or Laboratories, either in whoIe or in part, as may be placed under its directicm. 5. The committee shalI meet from time to the on caJ.I of the chairman and report its actions and recommendations to the executive committee. The committee on materials for aircraft, through its personn~l acting as a medium for the interchange of information regarding investigations on materials for aircraft, is enabled to keep in close touch with research in this field of aircraft de~elopment. Much of the research, especially in the development of Light alloys, must necessarily be conducted by the industries interested in the particular development and both the Aluminum Co. of America and the American Maaqesium Corporation are represented on the committee. In order to cover effectively the Iarge and -varied field of research on materials for aircraft three subcommittees were formed, as follows: Subcommittee on metak (Dr. G. ~. Burgess, chairman). Subcommittee on woods and glues (Prof. H. L. Whittemore, ohairman). Subcommittee on co~erings, dopes, and protective coatings (Mr. Henry A. Gardner; chairman). Most of the research in connection with the development of mat-eriaIs for aircraft is financed directly by the Bureau of Aeronautics of the Navy Department and the engineering division of the Army Air Service. The Bureau of Aeronautics and the engineering division of the Army Air Service in connection with the operation of tests in their own laboratories apportion and finanoe research problems on materials for aircraft to the Bureau of Standards, the Institute of Industrial Re- search, and the Forest Products Laboratory. 34 REPORT NATIOATAL ADVISORY COiWMi”TTEEFOR AERONAUTICS.

SUSCOMLMITTEEON METALS.

LIGET ALLOY$—DIJRALUMIN.

Flexura.1fatigue tests.—The ffexural fatigue machines for the testing of sheet duraIumin described in the reporh for 1922 have been in continuous and satisfactory operation through the past year at the Bureau of Standards, for the Bureau of Aeronautics of the Navy Depart- ment. Ninety-one specimens of seven different thicknesses (0.02 to 0.120 inch) and from two manufacturers have been tested. The number of specimens tested is smaller than was anticipated because it was found necessary to run tests up to two hundred million alternations of stress instead of from ten to twenty million, which had been found suff~cient for steels. The fatigue machines have been very free from disturbances. One machine has just been stopped after a 389-day nonstop run of two hundred million alternations. The check calibration of the machine on &Tovember 2, 1923, gave the same resuh as the original calibration on October 5, 1922. Sufficient information has been obtained to give a good idea of the fatigue characteristics of this material up to one hundred miIlion ah ernations of stress. Within that range no indication of an endurance limit has been found, This is consistent with published results secured with machined materials on rotating-beam machines at McCook Field and elsewhere. Impact fatigue tewls.-The impact fatigue machines were, after several preliminary machines had been designed and built, found to work satisfactorily. The specimen subject to tensile stresses was bent at an angIe of about 900 and clamped to the anvil. The tup struck tho middle of the specimen where it was bent. The portion of the specimen between the middIe and the ends was reduced to a width of one-half inch, the thickness being in all cases that of the origimd sheet as for the flexuraI fatigue tests. As in the preliminary trials, it was found that the specimens broke where they were struck by the tup, although the width there was one inch, and a metal protector was bolted to tlw middle of the specimen. When these protectors were used, failure occurred in the reduced portion for over 90 per cent of bhe specimens. The cast-iron anvil is supported on a block of concrete. It is usual in machines of this kind to support the anviI on springs, and mdess this is done comparable results wiIl Dot be obtained on machines built from the same drawings but supported on foundations offering different resistances. It was found, however, experimentally, that the three machines used for this work and placed side by side on the same floor did give comparable results. Tests of thin sheet steel such as is used in aircraft work will be made to compare with the results on duralum in. Theoretically, the stress in the reduced portion of the specimen is given by the formula.

in which E = modulus of elasticity-pounds per square inch, W= weight of tup — pounds. H = height of fall — inches. 1 = length of specimen between clamps — inches. a = area of reduced portion — square inch, In this formula, it is of course assumed that the specimen is one-half inch wide for its whole length, which is not the case. Some of the energy is dissipated in the floor and in other ways, Experiments showed that about 25 per cent of the energy is Iost if the specimens are thin (0.020 incld, and about 50 per cent if they are thick (0.120 inch). Allowing for this loss and computing the stress in the specimens shows that a large number of blows are required to cause failure if the stress is about 15,000 pounds per square inch. Graphs plotted from test results show that the number of blows is increased as the energy of the tup, and therefore the stress in the specimen, is decreased. The curves through these Takes show that a single blow causing a stress of about 421500 pounds per square inch would REPORT NATIONAL ADVEORY C!OMXITTEE FOP, AERONAUTICS. 85 rupture the specimen. This aggees with the results of tensiIe tests, as practically this same value was found for the yield point of the material. The resistance to impwt fatigue seems to be ~~her for specimens cut in the direction of rolling than for those cut perpemiicuhw to tbat direction. On some of the specimens tested in these impact machines, over one million blows were struck. Oi%erphysical properties. —To determine the other physiud properties of the sheet duraIumin, the tensile strength Io~~itudinally and across the rol@ direction, the Ericksen value, md the hardness (BrinelI, Roc.kweLI, and scleroscope) were measured. An apparatus was built to wrap the specimen, under a constant tension, fit around one cylinder, then in the opposite direction around another cylinder. The results of these tests were consistent and showed differences in the specimens that were more marked than those found by other tests. A tensile impact testi was aIso used which measured properties of the material that could not be found in any other way. It is evident that the usmd notched bar impact test can not be made on this thin sheet material This impact test showed that the energy absorbed was proportional to the thickness, and the same for longitudinal and crosswise specimens. — Twis on structural part$ for rigid airsliips.-!l?he tests described in the report for 1922, on the girders of the recentIy completed airship, U. S. S. Slkmandoai’i (Zl?-1), have Ied to a comprehensive series of tests on the durahruin charnels and an@es from which the girders are manufactured. The tests WW comprise compression tests on various shapes, thickness, md lengths, with contzoIIed failure simulating the conditions occurring in the girders. These will be correlated, thro~~h tests on short sections of the girders, with the resuIts already obtained on the full-sized girders. It is expected that these tests will make it possible to desibm for future airships lighter ~girders of equaI or greater strength. Tests of tsteelWing as columns and beams.-A special irrvestigation to determine the strength of steel tubing struts when sub jetted to combined transverse and column loading -was made for the Bureau of .lero~autks, Navy Department. The purpose of the investigation w-as to determine whether experiment aI data confirmed the approximate theory of struts subjected to these stresses. The physical properties of every section of tub~~ used was determined and a large number of tests were made on struts of different lengths with different intensities of transverse loading, . varying from that of a column with no transverse loading to that of a beam with no column load. A study of the conditions contribut~~ to the strer@h of steel tubing struts show that eccentricities result~~ from— 1. variations in wall thickness, 2. deviation from straightness, are wary importmb factors in determining the stren@h. These eccentricities -were accurately determined in this investigation by special measurements. The results of the investigation showed that experimental data does not corroborate the Mo P theory that as trut subj ected to transverse load~ms -@I faiI when the stress ~ X ~ approximates c the yield point where l.fo is determined by either of the commonly used formulas

(See MorIey, Theory of Structures, p. 309.) These form.das do not represent actual strut conditiom, the results indicat~~ that their use for short struts or struts with small side loads .— — may give dangpously high results. A modified rational formula based upon the consideration of the effect of eccentriciLy— 36 REPORT NATIONAL ADVISORY COIWMI’M’EEI?ORAERONAUTICS. where” e )‘ is the eccentricity, was found to give remarkable accurate resulte. The experimental data checks very closely -with computations by the modified formula and shows that it should be used when accuracy and safety are essential. The above modified rational formula reduces to the secant column formula

for struts with no side load, i, e., pure coIumns. The results of the column tests for which the eccentricities were accurately determined indicate that the column will fail when’ the ex tmme fiber stress, as determined by the secant column-formula is equal to the yieId point of the material. An empirical formula based on this formula in which the eccentricity “e” is taken as an average of the eccentricities in commercial tubing can probabIy be developed and used with reasonable accuracy and safety for determining the strength of columns.

SURCOMMITTEE ON COVERING DoPES AND PROTECWIVE COATINGS. During the past year rather extensive investigations have been carried on for the Navy Department in the development of fabrics, dopes, and protec~ive coatings, tit the laboratory of Mr. Henry A. Gardner. These investigations include the continuation of the work of past years on suitabIe fabrics for gas cells of rigid airships, very satisfactory results having been obtained during the past summer on exposure tests of experimental fabrics of low weight. These have remained very flexible and of almost constant low diflusion. Investigations have also been conducted on the development of fuek of the absolute alcohol-gasoline type. These studies also included an investigation of the effect of various fuels upon corrosion. A greah many tests have also been made upon the relative air and water corrosion of aluminum alloys, and methods of preventing such corrosion, together with the development of protective coatings for aIuminum sheets and aluminum alloy parts. Studies have also been included on the determination of the mosk suitable types of antifouling paints for bottoms of floats of aircraft that may remain moored for some considerable period of time in barnacIe-infested waters. At the Bureau of Standards extensive investigations ha-ve also been made during the past year in the development of experimental gas cell f abrics f or rigid airships, most promising initial resuIts having been obtained with certain new types that have recently been exposed. The Bureau of Standards is aIso at the present time making extensive investigation of the effects of clifferent ways of preparing the rubber and of the addition of various materials to rubber that is used in the manufacture of airship fabrics, to determine the effect upon the lowering of permeability, etc. The bureau is also cooperating in the various work being done in the production of various coatings, H has been examining various types of fabrics submitted by the Navy Department for permeability and strength tests. I-thas also been active in the examination of dopes. A multicross system of dead-weight loading was ernployedby the textile section of the 13ureau of Standards to test the load-deformation characteristics of the doped outer cover cloth specified for use on the ZR–I. These tests required several thousand observafiions and were conducted under standard humidity conditions, The purpose -was to supply data to be used in calculations on the contribution of the outer cover cloth to the structural strength of the airship. The data showed further that this type of doped fabric under load changes continuously in physical characteristics with time; however, two weeks’ loading is generally sufficient to obtai~ a fairly constant moduIus. A preliminary report on general characteristics and a final report covering changes occurring during one week were made. The tests were continued for five weeks.

SIJSCOMMITTEE ON WOODS AND GLUES.

The Forest Products Laboratory of the Department of Agriculture conducts practically all investigations on the application of woods and glues to aircraft construction. Most of the investigations are undertaken at the request of the Bureau of Aeronautics, Navy, or the engineering division of the Army Air Service. The following are some of the more importan~ investigations. REPORT NATIONAL ADVISORY COMXITTEE FOR ARRO?IAUTICS. 3’7

Causea of bra.s%new of med.-The Forest Products Laboratory have tested over 500 specimens in the tou@ess machine of ash, spruce, oak, tmd black walnut, some of which were normal and some of which were brash, i. e., broke at low Ioads with little deformation. The data on the oak and mdnut have not been fully amdyzed. The information so far obtained shows that brashness, at least in the ash and spruce tested, does not depend on the obvious st.ructud characteristics of fihe wood, such as width of annual rings, proportion of summer wood, thickness of fiber walls, number of meddlary rays, etc., but is apparently due to something more obscure, such as the physicaI or chemical structure of the cell walls. Ikcelopment of wate~proof glues .-The investigation of waterproof glues has been continued during the year by the Forest Products Laboratory. Enowle~~e on this subject has been considerably increased by a study of some ~atural and artificial gums and resins which may be suibabIe for use as adhesives. A blood albumin glue has been developed which can be used without hot pressing and this on a laboratory scale has pro-veal practically waterproof. Before recommending it for general use, ii wiIl be necessary to find the best method. of using it, for heavy stock. The cost of the glue is, at present, higher than commercial glues but it is probable that further invesfiigat.ion VW develop a composition which w-M replace other glues. Use of plywood in wing 6eams.—The investigations of the Forest Products Laboratory, during the past year, on the shear~w strength of plywood, shows the desirability of using the plywood with the face grain at an angle of about 45° with the length of the beam to obtain the greatest strength in the structure. i% series of tests was made on beams, approximating the upper front BS-1 w-irg beam section, to determine the best way to use pl-~ood in beams of this size. These tests together with observations on numerous other types of beams, led t-o the conclusion thtit in ihe design of either plywood box or I beams a web thickness 25 per cent greater than that calculated to give equal likelihood of fafiure b y shear or compression, wilI give the beet results. The results further demonstrated that in thee-ply webs with the grain at 45° to the length of the beam the t,wo face plies shouId be of equal thickness and their combined thickness should equal that of the core in order to prevent side bucklirg of the beam under Ioad. This affords symmetry of construction and avoids the unequal distribution of stresses and greater tendency to IateraI buckling which accompanies a lack of balance between core and faces. Reports have been . issued on both series of tests. In$uence of tsvkrhw,molds, and decay on properties of wood.—This study should furnish data on the effect of stains, molds, and decay on the principal woods used in the airplane indu@ry. Means for diagnosing early stages of decay should be worked out. Methods for preventing or controlling decay in airplane timber should be formulated. Previous to June 30, 1922, this project has been almost entirely supported by the Bureau of Plant Industry. ” Approximately 1,200 tests had been run of Sihka spruce and 800 tests on Dm@s b. These tests included static bendirg impact bending, compression parallel, .— shear and hardness tests on both green and dry sticks. The project is now be~~ carried largely by the Arm-y and Navy Air Services with certain assistance from the Bureau of Plant Industry. Some 1,400 toughness tests ha-re been run on green Douglas fir infected with fungg which are common to both Douglas fi and Sitka spruce. In the course of this year S,500 cultures have been run to determine which of the tested sticks were sound and which were infected. Cor- relation of the results of the mechanical tests has been started for the Do@as fir. The results so far show a marked difference in the effect produced by the different fungi. The conditions under which the yeUow@ of oak airplane lumber occurs have been studied in a set of experiments in which the boards were yelIowed by artificial inoculation. Form factors for wing beams.-The Forest Products Laboratory have completed the fu~da- mental study of form factors and stresses in bending which has resulted in the development of formulas for accurately computing the form factors of various sections. The fundamental work undertaken on the influence of form on the strength and stiffness of woodem beams has been completed during the present year. A report covering Part 1 of 3$ REPORT ITATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. this study, entitled “Deflection of Beams with Special Reference to Shear Deformations,” and Part II, “Form Factors of Beams Subjected to Transverse Loading Only,” has been prepared. The work has also been completed on Part III of this study entitled “ Stresses in Wood Members Subjected to Combined Column and Beam Action, ” In the light of the data covered in Part 11, definite conclusions have been arrived at regarding the maximum stress in members subjected to combined cohmm and beam action for various ratios of compressive to total stress. The tests which have been made are conclusive regarding the variation of stress at maximum load for various ratios of compressive to tottil stress, and these date, are now being correlated with the theoretical considerations involved. The above mentioned report in three parts, will be published as Technical Reports of the National Advisory CommitLee for Aeronautics. Toughness tests of airplane woods.—1n connection with the inspection of wood for airplanes, particularly those species used for propeller constructio~, a need has been felt for a simple test which could be applied to each piece of wood to determine its acceptability. To meet this need a machine, utilizing the pendulum principIe but applying the load by means of w strap operating over a drum, was developed for testing relatively small specimens witL. a sing]c swing of the pendulum, This test gives a good indication of the toughness of a specimen, and the character of the failure is of further value in estimating the quality of the wood. IL WOUh! appear that this test is more practicable than the specific gravity Iimi~ation now adoptml as standard acceptance for aircraft wood, and at the same time affords a more reliable criterion of the strength. Torsion in box and other 6eam sections.—This investigation was undertaken by t?.mForest Products Laboratory at the request of the Bureau of Aeronautics, Navy, as very little datz were avai.labIe on the torsional strength of b e~ms of various cross sections and no torsional formulas which could be used in designing members of other than soIid circular sections with any degree of accuracy. These tests that have been made fully support the conclusions dr~wn from a consideration of the principles of mechanics to the effect that the most efficient torsion member is a tube of circular sectiori whose walls consist of several thicknesses of thin ve,ncer wound in alternating spirals. However, there are ‘two principal obj ectiom to the uso of such sectiom, viz: (1) the difficulty of buikling them, and (2) ihe di~lculty of attaching other menl- bers to them. While these difficulties are not insurmountable, it is considered preferable from the standpoint of convenience, rapidity, and cost of production, to use torsion members of box section of rectangular or at least quadri~ateral outline. During the present and preceding fiscal years a number of tests have been made in an attempt to determine how to proportion the various parts of box beams for maximum efficiency and to derive rules or formulas for the construction of beams to meet a given strength require- ment. These tests have indicated that sections now used are probably not the most efllcient and that the formuIas and factors used in design are of uncertain applicability. A report of this work will be written during the present fiscal year. E~ect of isolated factors on seasoning.-This investigation has been continued by the ‘“ Forest Products Laboratory and during the present fiscaI year the experimental work on birch was completed and the finzd report on ash prepared. Work was also started on another species. A fundamental equation has been developed showing the relation between the moisture content and drying rate. This is an important basic formula and its deveIopmenL will aid very materially in the perfection of drying methods and schedules for aircraft.

‘TECHNICAL PUBLICATIONS OF THE COMMITTEE.

On recommendation of the committee on publications and intelligence, the National Ad- visory Committee for Aeronautics has authorized the publication of 27 technical reports during the past year. The reports cover a wide range of subjects on which re%earch has been conducted under the cognizance of the various subcommit teee, each report having been approved by tho subcommittee concerned and recommended to the executive commit tm for publication. Tho technical reports presented represent fundamental research in aeronautics carried on at different aeronautical laboratories in this country incIuding the Langley Memoritl Aeronmtical REPORT NATIOXAL ADTISOEY COX3HTTEE FOE AERONAUTICS. 39

Laboratory, the aeronautical laboratory at. the WAinggton Navy Yard, the Bureau of Standards, the Forest Products Laboratory, the Stanford T_hiwrsit.y, and the Massachusetts Institute — of Technology. To make immediately availabIe technimd information on experimental and research problems, the A’ationaI Advisory Committee for Aeronautics has authorized the issm.nce in mimeographed form of another series known as “ TechnicaI L’otes,” of which 45 have been issued duri~~ the past year. A list of the technical notes issued dur%g the fiscaI year folIows the summary of technical reports. The. office of aeronautical intelligence, in addition to issuing technical reports and technical notesz has issued traditions and reproductions of importanh technical articles of a mis- cehneous character. These have been issued in mimeographed form, and the number of requests for and the importance of the-se papers resulted in an action of the executive committee authorizing the committee orLpublications and intelligence to issue tradatioris and technical articIes to be known as “ TeehnicaI Ueruorandums 1} of the A’ational Advisory Committee for .keronautics. In accordance tith this authoriztitioq the committee has issued 91 teh.ical memorandums on subjects that were of immediate interest not onIy to rmeamh laboratories but. also to airpkme manufacturers. A list of tech,nical memorandums issued during the year follows the list of technical notes. Summaries of the 27 technical reports issued durkg the past year, and lists of the technical notes and technical memorandums issued durirg the past year follow.

Stll~&.RY OFTECE3KTC.UREPORTS.

The first annuaI report of the National Advisory Committee for Aeronmtics contained Technical Reports A“os. I to 7; the second annuaI report, A’os. 8 to 12; the third annuaI report, ~Nos. 13 to 23; the fourth annual report, h’os. 24 to 50; the fifth annual reportl NTOS.51 to S2; the sixth annual report, h’os. 83 to 110; the seventh annual report, Nos., 111 to 132; the eighth mnuaI report, ATOS.133 to 15S; and since the preparation of the eighth annual repor~ the committee has issued the foIlowing technicaI reports, A’os. 159 to 185: Report No. 159, enfitIed “Jet Propulsion for Airplanes,” by Edgar Buckingbam, Bureau of StancIards.-This report is a description of a method of propeuing airplanes by the reaction of jet propulsion. .kir is compressed and roked -with fuel in a combustion chamber, where the mixture burns tit. constant pressure. The combustion products issue through a nozzIe, and the reaction of the jet constitutes the thrust. Data are a~aiIabIe for an approximate comparison of the performance of such a device with that of the motor-dri~en air scre-iv. The computations are outIined and the resuIts given by — tables and curves. The reIati~e fueI consumption and w-eight of mzchinery for the jet, decrease as the flying speed increases; but at 250 miles per hour the jet -would still take about four times as much fueI per thrust horsepower-hour as the air screw, and the power pIant would be heavier and much more complicated. Propulsion by the reaction of a simple jet can not compete, in any respect, with air screw ------=-- propukion at such flying speeds as are now in prospect. Report .Yo. 160, entitled “An Airship Slide Rule,” by E. R. Weaver and S. F. Pickering, Bureau of Standards. -This report describes an airship sIide ruIe dei-eIoped by the gas-chemistry section of Lhe Bureau of Standards at the request of the Bureau of Engineer&a of the RTavy Department. The de~elopment of this sLide rule was requested by the Navy became of the suceesfuI resuIts which had been reported by the Scot t-Twee3 rule which had been deveIoped and used by the British naval air service. It is intended primarily to gi~e rapid soIutions of a few problems of frequent occurrence in airship ~a-rigationj but it can be used to ad~antage in solv@ a great v-ariety of probkms, involv@ rolumes, lifting powers, temperatures, pressures, altitudes, and tke purity of the baUoon gzs. =11.~~ 40 REPORT A~ATIONAL AD171SORYCOMMITTEE FOR AERONAUTICS.

The ruIe is graduated to read directIy in the units actually used in making obsmvntions, constants and conversion factors being taken care of by the length and locations of the scales. In order to simplify as much as possible th~ manipulation of the rule, absolute accuracy has in some cases been sacrificed to convenience. Generally this has been necessary only in those cases in which the data upon which the computations will be based are not subject to accurate observation. It is thought that with this ru~e pracLicaIIy any problem likeIy to mise in this class of ~vork can be readily soIved after the user has become familiar with the operation of the ru~e, and that the solution will, in most cases, be as accurate as the data wmrant. Report No. 161, entitled “ The Distribution of Lift over Wing Tips and Ailerons, ” by David L. Bacon, Langley Memorial Aeronautical Laboratory .—This investigation was cmricd out, in the 5-foot wind tunnel of the Langley Memorial Aeronautical Laboratory for the purpose of obtaining more compkte information than was heretofore a-r-aiIable on the distribution of lift between the ends of wing spars, fihe stresses in ailerons and the general subject of airflow near the tip of a wing. It includes one series of tests on four models without ailerons, ha~ing square, ellip~ical, and raked tips respectively, and a second series, positively and negatively raked wings, with aiIerons adjusted to different settings. The results show that negatively raked tips give a more uniform distribution of tiir pressure , than any of the other tkree arrangements, because The tip vortex does not disturb the flow at the traiIing edge. Aileron loads are found to bc decidedIy less severe on wings with ncgntive rake than on those with positive rake. The data are presented in such form m to permit dircc~ app~ication to the calculation of aiIeron and wing stresses and aIso to faciIitzte the proprr distribution of load in sand testing. Contour charts show in great detail the complex distribution of Iift over the wing. Report fiTo. 162, entitled “Complete Study of the Longitudinal Oscillation of a YE-7 Air- plane,” by l?. H. Norton and W. G. Brown, Langley Memorial Aeronautical Laboratory.—This investigation was carried out in order to study .as- closely as possible the beba-rior of an airpIane when it was making a longitudinal oscillation. The air speed, the altitude, the angle with the horizontal and the angle of attack were all recorded simultaneously and the resulting curves plotted to the same time scale. The results show that all the curves me Yery C1OSCto damped sine curves, with the curves for height and angle of attack in phase, thai for angle with the horizon leading them by 18 per cent and that for path angle leading them by 25 per cont. Report No. 163, entitled “The Vertical, Longitudinal, and Lateral Accelerations Expe- rienced by an S, E. 5A Airplane While Maneuvering,” by F. H. h~orton and T. Carroll, Langley Memorial Aeronautical Laboratory .—This investigation was undertaken for the purpose of measuring the accelerations along the three principal axes of an airplane while it was maneuvering. The airpIane selected for this purpose was the fairly maneuverable S. E. 5A and the instruments used were the hT. A. C. A. three component accelerometer and the NT.A. C. A. recording air speed meter. The results showed that the normaI accelerations did not exceed <.(N g., while the Iateral and longitudinal accelerations did not exceed 0.60 g. Report No. 161, entitled “The Inertia Coefficients of an Airship in a l?rictionless Fluid,” by 13. Bateman, CaIifor~ia Institute of Technology.—This report deaIs with the in-vestigation of the apparent inertia of an airship hull. The exact solution of the aerodynamical problem has been studied for hulk of various shapes and special attention has been given to the case. of an ellipsoidal hull. In order that the results for t~lis last case may be readily adapted to other cases, they are expressed in terms of the area and perimeter of the largest cross section perpen- dicular to the direction of moticm by means of a formula involving a coefficient K ~vhieh varies only slowly when the shape of the hull is changed, being 0.637 for a circular or elliptic disk, 0,5 for a sphere, and about 0.25 for a spheroid of fineness ratio 7. For rough purposes it is sufficient to employ the coefficients, originally found for ellipsoids, for hulls otherwise shaped. I’i%en more exact values of the inertia are needed, estimates may be based on a study of the way in which II varies with different characteristics and for such a study the new coefficient possesses some advantages over one which is defined with reference to the volume of fluid displaced. REPORT NATIONAL ADVISORY C03LMIT’IXE FOR AERONAUTIC% 41

The case of rotation of an airship hti has been investigated ako and z coefficient has beeri defied with the same advantag~ as the corresponding coefficient for rectilinear motion. Report N-O.163, entitled “ Diaphrams for Aeronautic Instruments,” by Mayo D. HerSe-y, Bureau of Standards.-This in-wstigation was carried out at the request of the ~ational .4d-risory Committee for ~erormutics and comprises an outLine of historical developments and theoretical prineipks, together with a discussion of expedients for making the most effective use of exkting diaphrams, and a summary of experimental research problems. FIe.sible diaphragms actuated by hydrostatic pressure form an mential element of a great variety of instruments for aeronautic and other technical purposes. The various physical data needed as a foundation for rational methods of diaphragm desiam have not, however, been a-raiIable hitherto except in the most fragmentary form. Report No. 166, entitled “The Aerodynamic P1ane Table,” by A. F. Zahm, Bureau of Con- struction and Repair, Navy Depa.rtment.-This report gives a description and the use of a speciaIIy designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory} and for misce~aneom truing operation% there is frequent need for a specially equipped pIane tabIe. F’or exarnpIe, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets = of a strut, air&p hulIr or other careftiy formed figure may require exact calipering. &ain, a cumpIete airpIa~e model may have to be adjusted for correct incidence at alI parts of its sur- f~ces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on E planing or milLing machine; but if frequent, justifies the protiion of a special tab~e. For this reason ik was found desirable in 1918 to make the tabIe described in this report and to equip it with such ga~mes and measures as the work should require. Report No. 167, entitled “ The Measurement of the Damping in RoJI on a JN4h in Flight, ” by F. H. \rorton, LangIey lfemorial Aeronautical Laboratory .-This investigation -was carried ou~ by the A“ationaI .ld~isory Committee for Aeronautics for the purpose of measuring the value of LP in flight. The method consisted in flying with heavy weights on each wing tip, suddenly reIea@ one of them, and aIIowing the airplane to roll up to 90” with controls held in neutral while a record was being taken of the air speed and anguku- veIocity about the I axis. The results are of interest, as they show that the damping found in the wind tunnel bJ- the method of small oscillations is in general 40 per ceni higher than the damping in flight, .$t 50 m. p. h. the fight curve of LP has a high peak, which is not. indicated in the mode] results. It is also shown that at this speed the Iateral m.a~eu~erability is low. Report A’o. 16S, entitled “The GeneraI Efficiency Cum-e for Air Propellers,” by Walter S. DieId, Bureau of Aeronautics, United States Navy.-This report is a study of propel~er efficiency b=ed on the equation. ‘v -.— K= COL(@ +y) ()r ND speed of advance. re~olutions per unit. of time. diameter of the helix described by the particular element under consideration. tan –1 “L ()T iND tan –1 D ()L It is sho-wn that this formuIa maybe used to obtain a “general efficiency curve” in addition to the -well-known maximum eiliciency cur-re. These two curves, when modified somewhat by experimental data, enabIe performance calculations to be made without detaiIed knowledge of the propelIer. The curres may also be used to estimate the improwment in efficiency due to reduction gearing, or to judge the performance of a new propeller design. Report No. 169, entitIed” The Effect of Airfoil Thickness and PIan Form on Lateral Control,” by H. 1. HocJt, La@ey MemoriaI Aeronautical Laboratory.-This investigation was carried 42 REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. out for the purpose of’ determining the effectiveness of aiIerons and tests were made on six model airfoils in the NTO.I wind tunnel of the NationaI Advisory Committee for .%eronautics. The method consisted in measuring the roIIing moments and aileron moments in the ordinary way. lrI addition to this the wing was allowed to spin freeIy about, an axis in the direction of the air flow and the angular veIocity measured. The resuIte show that the thickness of the airfoil has very Iittle effect on either the rolling moment or the hinge moment, but that the tapering in plan form somewhat decreases the rolI- ing moment and hinge moment, although the resulting ei%ciency is somewhat higher for the tapered wings. The airfoil tapered in plan form, however, shows practically no fa~ling off in the rolling moment at the criticaI angle of attack, whereas the wings of rectangular plan form show a marked dropping off in the rolling moment at this point. This indicates that it is pcs- sible to obtain good latertil control with small aiIerons at low speeds if ~he plan form is tapered. The rotational speed of the different airfoiIs is practically the same for all of the sections tested. Report hTo. 170, entitled “A Study of Longitudinal Dynamic Stability in Flight,” by F. H, Norton, Langley Memorial Aeronautical Laboratory, —This investigation was carried out by the aerodynamic staff of the National Advisory (!ommittee for Aeronautics for the purpose of studying experimentally the longitudinal dynamic stability of airplanes in flight. The airpIanes selected for this purpose were a standard rigged VE-7 advanced training airpIane and a JhT4h with special tail surfaces, The airplanes were caused to oscillate by means of the elevator; then the Longitudinal conirol was either locked or kept free while the oscillation died out, The magnitude of the oscillation was recorded either by a kymograph or an airspeed mete~. The results show that the engine speed has as much effect on the period and damping as the airspeed, and that, contrary to theory as deveIoped for small oscilIations~ the damping decreased at the higher airspeeds with closed throttle. Report No. 171, entitled “Engine Performance and the Determination of Absolute Ceiling, ” by V/alter S. Diehl, Bureau of Aeronautics, Navy Department, —This report was prepared for the National Advisory Committee for Aerommtics and contains a brief study of the variation of engine power with temperature and pressure. It is shown that for the conventional engines “ 1.15 BHPa ~ ()Po when temperature and R. P. M. are held constant and that

T -0.50 BHPa ~ () o when ~ressure and R. P. M. are held constant. Combining these in the standard atmos~hereL (N. A: C. A. Report No. 147 and TechnicaI Note NTO.99) g~ves.

BHPa ~ ‘“055 ()Po for constant R. P. M. The variation of R. P. M. with altitude is then found from the flight tests reports of the United States Army Air Service to be 0.10 Na -–P ()Po for the usual case, or constant in certain special cases where the engine is provided with adequate throttle control. These relations are sufficient to determine the variation of BHP in standard atmosphere. The variation of propeller efficiency in standard atmosphere is obtained from the general et%ciency curve which is developed in N. A. C. A. Report No. 168. The variation of both power available and power required are then determined and curves plotted, so that the absolute ceiling may be read directly for any known sea-level vaIue of the ratio of power available to power required. REPORT NATION-AL ADVISORY COMMIITEE FOR AERONAUTICS. 43

Report ATo. 172, entitled “Dynamic Stability as Affected by the Longitudinal Moment of Inertia, ” by Edwin B. Tllison, Har~ard University.-In a recent Technical Note (No. 115, October, 1922] of the hTationaI Advisory Committee for Aeronautics, Norton and CarrolI have .— reported experiments showirg that a relatively large (15 per cent) increase in longitudinal moment of inertia made no noticeable difference in the stability of a standard S. E. 5A airpIane. They point out that G. P. Thomson, “Applied Aeronautics,” page 20S,stated that an increase in longitudinal m.omenk of inertia would decrease the stability. Neither he nor they make any theoretical forecast of the amount of decrease. Although it is diEEcult, on account of the complications of the theory of stabfity of the airpIane, to make any accurate forecast, it may be worth whiIe to attempt a discusion of the matter theoretically with reference to finding a rough quantitative estimate. Report .To. 179, entitled “ Reliable Formulae for Estimating Airplane Performance and the Effects of Changes in Weight, Wing Area, or Power,” by Walter S. Diehl, Bureau of Aero- - -— nautics, United States hTavy.-This paper, which was prepared for publication by the hTational Advisory Committee for Aeronautics, contains the derivation and the verification of formulae for predicting the speed range ratio, the initiaI rate of cIimb, and the absolute ceiling of an air- pIane. It is shown that the ratio of the maximum speed Yw to the minimum spee’d Y~ is given by

where ~~ is the maximum propeller efficiency and El is a constant with an average value of ~0.~0 when ~ ~ ~ ~f. p. H. and ~ ~ & lb./BHpa

The rate of climb at sea level, CO,is given by

IL where ~ is the overall value for the airpIane at the angle for best climb (ma.timum value of ~ () is to be used) and ~ is a constant found to be

= = JT’ *.27 2 ()1’, “ The absohte ceiling is given indirectly by L HP.. “ ()D HT. = ;.\’ S.&y (

K, having an average value of 61.7 when V, is in 31. P. H. and ~ is in Ib./BHP. The absolute HPao ceiling is obtained by reference to the usual curves of absolute ceiling against the ratio —. HPro These curves are gi~en in National Advisory Committee for Aeronautics Report ATO.171. Standard formulae for service ceihg, time of cJimb, cruising range, and endurance are also given in the conventiona~ forms. Report No. 17A, entitIed “The SmaLl Angular Oscillations of Airplanes in Steady Flight,” by F. H. Norton, LangIey lf emoriaI Aeronautical Laboratory.—This investigation was carried ouh by the hTational Advisory Committee for Aeronautics at the request of the Arm-y A-h-Service to provide data concerning the small angukr oscillations of several types of airplanes in steady flight Uder various atmospheric conditions. The data are of use in the desigg of bomb sights and other aircraft instruments. The method used consisted in flying the airplane steadiIy in 44 REPORT NATIONAL AD~71SORYCOMMITTEE FOR AERONAUTICS. one direction for at least one minute, while recording the angle of the .airpkme with the sun by means of a Iiymograph. The results show that the oscillations differ but little for airplanes of various types, but that the condition of the atmosphere is an important factor. The average angular excursion from the mean in smooth air is 0.8° in pitch, 1.4° in roll, and 0,9° in yaw without special instruments to aid the piIot in holding steacly conditions. In bumpy air the values given above are increased about 50 per cent. Report A~o. 175, entitled “Analysis of W. F. Durand’s and E. l?. LesIey’s Propeller Tests,” by Max M. Munk, National Advisory Committee for Aeronautics. —This paper is a critical study of the results of propeller model tests with the view of obtaining a clear insight into the mechanism of the propeller action and of examining the soundness of the physical explanation generally given, The nominal slip-stream velocity is pIott ed against the propeller tip-velocity, both measured by the velocity of flight as a unit. Within the range corresponding to conditions of flight, the curve thus obtained is a straight line. Its inclination depends chiefly on the effective blade width, its position on the effective pitch. These two quantities cm therefore be determined from the result of each propeller test. Both can easily be estimtited therefrom for new propellers of similar type. Thus, a simple method for the computation of propellers suggests itself. The slip curve mentioned is not a straight line along its entire length. At a small relative tip ve~oeity it is bent up, because the lift curve of the bIade sections used is bent up that way at small lift coefficients. At a certain high relative tip velocity the slip curve shows a break and runs then straight again but at a different slope. The slope is increased so that at progress zero the propelIer develops a larger thrust than could be expected from the magnitude of the thrust in flight. Report hlo. 176, entitled “A Constant Pressure Bomb,” by F. W. Stevens, Bureau of Standards. -This report, prepared for publication by the hTational Advisory Committee for Aeronautics, describes a new optical method of unusual simplicity and of good accuracy suit fible to study of the kinetics of gaseous reactions. The de-rice is the complement of the spherical bomb of constan~ volume, and extends the applicability of the relationship, pv = RT for gaseous equilibrium conditions, to the use of both factors p and v. The method substitutes for the mechanical complications of a manometer placed ai some distance from the seat of reaction the possibility of a~lowing the radiant effecfs of the reaction to record themselves directly upon a sensiti~e film. It is possible the device maybe of use in the study of the photoelectric effeck Of radiation. The method makes possible a greater precision in the measurement of normal flame velocities than was previously possible. An application of the method in the investigation of the rc]ationship between the flame veIoci6y and the concentration of the reacting components, for the simple reaction of 2C0 + Oz = 2C0,, shows that the equation

~= ~2:co,- describes. the rezction. An approximate analysis shows that the increase of pressure and density ahead of the flame is negligible until the velocity of the flame approaches thai of sound. Report Are. 177, entitled “The Effect of Slip Stream Obstructions on Air Propellers, ” by E. P. LesIey and B. M. Woods, Stanford lJniversifi~.-Thc screw propeIler on airplanes is usually placed near other objects, and hence its performance may be modified by them. Results of tests on propellers free from slip stream obstructions, both fore and aft, are therefore subject to correction, for the effecfi of such obstructions and the purpose of the investigation was to determine the effect upon the thrust and torque coefic.ients and efficiency, for previously tested air propellers} of obstructions placed in the slip stream, it being realized thut such previous tests had been conducted under somewhat ideal conditions that are i.mpracticnMe of realization in flight. REPORT ATATI(2NAL ADTLSORY COMMITTEE FOR AEROLTAUTICS. 45

.&t the start of this in-restigation, it was planned to use obstructions representative of the nose of the fuseIage, of radiators, or of other parts of an airplane structure] but a consideration of the wide variety of forms thus dfi~ed led to the s~ection of simple geometrical forms for the initial investi~ation. Such forms offered the advantage of easy, exact reproduction at another time or in other laboratories, and it was believed that the effects of obstructions usually encountered might be deduced or surmised from those chosen. .l? a systematic md comprehensi~-e study of the effects of scale and quaIity of turbulence will be necessary to complete the problem, as this phase was giren onIy general treatment.. LIST OF TECHNICAL NOTES ISSLXO DLIUXG THE PAST TIME. No.

I I .5. The Effect of Longitudinal Moment of Inertia upon Dynamic Stability. By F. EL Norton and T. (lkirro~, N. A. C. A. II 6. F–5–L Boat Seaplane-Comparative Performance with Direct Drive and Geared Engges. By W. S. Diehl, Bureau of Aeronautics, Navy Department. I I7. The Synchronization of h’. A. C. A. Flight Records. By W. G. Brown, N. A. C. A. I IS. F–5–L Boat Seaplane-Performance Characteristics. By W. S. DiehI, Bureau of .iero- nautics, hTa~ Department. I I9. The EIiminat ion of Dead Center in the Cent rob of Airplaries with Thick Sections. By T. Carroll, N. A. C. A. 1?0. A Preliminary Study of Airplane Performance. B; F. H. Norton and W. G. Brown, N. A. c. A. 121. Further Information on the Laws of Fluid Resist ante. By C. Wieselsberger. Translated from PhysikaIische Zeitsclmift, T’ol. 23, 1922. . 12?. The Determination of the Ar@es of Attack of Zero Lift and of Zero Moment, Based on Mink’s lntegraLs. By Max M. Munk: N. A. C. A. 123. .&n OpticaI Altitude Indicator for Night Landing. By J. A- C- Warner, Bureau of St a~d- ards. 124. Domwash of Airplane Wings. By Max M. Munk and Gunther Carno. Transited from Technische Berichte, YoI. ~, No. 1 (191 S). 125. Results of Experimental Flights at High Altitudes with DaimIer, Benz, and Maybach Eng~es to Det~fie Xfiture Formation and Heat Utilization of Fuel. By K. Kutz- bath. Translated from Technkche Berichte, TTO1.HI, No. 1 (191 S). 126. Absolute Dimensions of Karman Vort~~ Motion. By Werner Heisenberg= Translated from Ph@kaIische Zeitscbrift, Sept. 15, 1922. 127. The Air Propeller, Its Strength and Correct Shape. By H. Dietsius. TramIated from Technische Berichte, Vol. HI, No. 2 (1918). 48 REPORT NATIONAL AD~ISORY COMMITTEE FOR AERONAUTICS.

h~o. 128. Test on an Airplane Model, AEG D 1, of the Allgemeine Elekhicitats Gesellschtif t, AEG, Airplane Construction Section Conducted ai the Gottingen Model Testing Laboratory for Aerodynamics. By Max M. Munk and lViIhelm Molthtm. Translated from Technische Berichte, Vol. III, No. 2 (1918). —.

129. Notes on Aerocllmmnic Forces on Airship Hulk. By 1.. B. Tuckermfin, Bureau of Stand- ards, 130. Model Supports znd Their Effect on the Results of Wind Tunnel Tests. By David I.. —. Bacon, N. A. C. A. 131. Variation in the Number of Re-rolutions of Air Propellers. By W. .Achenb~ch, Trrins- latecl from Technische Berichte, Vol. III, No. 2 (1918). 132.The Increase in Dimensions of Airplanes—Weight, Area, and Loading of Wings. By E. 12verling. Transited from Technische. Berichte, Vol. 111, No. 2,(1918). 133.Disturbing Effect of Free Hydrogen on Fuel Combustion in Internal (’ombust ion Engines, B37A Riedler. Translated from Technische Berichte, Vol IH, No. 2 (191 s). 134, Standardization and Aerodynamics. By Wm. Knight, L. Prandtl, v. Karman, G. Cos- tanzi, W. Margoulis, R. Verdu.zio, R. Katzmayr, E. B. Wolffj and A. F. Zahm. Talien from Aerial Age, June 20 and Oct. 3, 1921; Jan. 2, Feb. 20, Mar. 6, Apr. 3, May 8, June 19, Sept. and Dec., 1922. 135.Memuring an Airplane’s True Speed in Flight Testing. By TV. G. Brown, N. ii. C. .\. 136. Is There ih~ AvaiIabIe Source of Heat Energy Lighter Than Gasoline? 13y P. Meyer. Translated from Technische Berichte, VO1. 111, No. 3 (191 S). 137. Fabrics for Covering Airplane Wings. By A. ProII. Transited from ‘llcl~nischc Be- richte, Vol. 111, No. 3 (1918). 138. Determination of the Value of Wood for Structural Purposes, By Richard 13fiunlmn. ~ Translated from Technische Berichte, l’oI. 111, No. 4 (1918). 139. Influence of Ribs on Strength of Spars. By L. BalIenstedt. Transited from Tcchnischc Berichte, Vol. 111, No. 4 (1918). 140. General Theory of Stresses in Rigid Airship ZR-1. By W. Watters Pagon. 141. Experiment with a Built-in or Fuselage Radi&tor. By C. Wieselsberger. Translated from Technische Berichte, Vol HI, No. 4 (191 S). 142. Adaptation of Aeronautical Engines to High Altitude Flying. By K. Kufzbmh. Trans- ited from Technische Berichte, Vol. 111, No. 4 (1918). 143. Calculations for a Single-strut Biplarie with Reference to the Tensions in the Wing Bracing. By O. Blumenthal. Translated from Technische Berichte, Vol. 111, No. 5 (1’218). 144, hTotes on the Design of Ailerons. By W. S. DieM. Bureau of Aeronautics, Navy De- partment. 145, Aeronautical Instruments. By Kurt Bennewitz. Translated from Technische Bcrichte, 170~. ~~~, No’. 5 (1918). 146. The Fairing of Airfoil Contours. By Edward l?. Warner, Massachusetts Institute of Technology. 147. Speed hleasurements Made by Division “:1” of the Airplane Directmate (F]ugzeugmei- sterei), Subdivision for FIight Experiments. By V. Heidelberg and A. HoIzel. Trans- lated from Technische Berichte, VO1. 111, No. 5 (l~s). . 148,The Flexible Mounting of an Airplane Engine. 5Y K. Kutzbach. Trans~atcd from. Technische Berichte, VOI. 111, No. 4 (1918). 149.MIuence in the Selection of a Cycle for Srwdl l~igh Speed Engines Rwming on SoIid or Airless Injection With Compression Ignition .- By Robertson Matthews, N. ii. C, A. 150. Notes on the N. A. C. A. Control Force Recorder. By H. J. E. Reid, N. A. C. A. 1.51. Tests on BuiIt-up AirpIane Struts Having Initial Tension in Outside Fibers. By T. A. Scwamb and C. S. Smith. 152. Thrust a~d Power Required in Climbing. By Georg Koenig. Translakid from Technische Berichte, Vol. 111, No. 5 (1918). REPORT N7ATIONAL ADTISORY COM311TTEE FOR AERO&”AUTICS. 49

Ho. 153. Flight Characteristics. By Capt. Student. Translated from Technisehe Berichte, Vol. 111, NO. 6 (191S~. 154. .An lns~rlment for Re;ording the Position of Airplane Control Surfaces. By K. M. Ronan, N. A. c. A- 155. Regulatiom Governing the issuance of Certificates of Airworthiness of Aircraft. in France. Translated from BulIetin de la Navigation Aerienne, March, 1923. 156. The N. A. C. A. Recor&g Tachometer and Angie of Attack Recorder. By H. J. E. Reid, N. A. c.A. 157. An Impulse Motor for I)riting Recording Instruments. By W. F. Joachim, N. A. C!. A. A.naIysis of Dr. Schaffran’s PropeIler Mode] Tests. By Max 31. Munkj h?. A. C. A. 15s. — 159. The Time Lag and Interval of Discharge with a Spring Actuated Fuel Injection Pump. By Robertson Matthews and A. W. Gardiner, AT.A. C. A.

LIST OF TECHNICAL MEMOR.INDI.MS ISSUED DURING THE PAST YEAR.

140. ~eroclynamic Computation of Gliders. By- K Schrer&. Translatecl from FIugsport, Jfay 21, 1922. 141. lliniature &rplanes. By Edward P. warner. 14.~- The Disposal of l~tary ticraft. By Edward P. warner. 143. What Retarcls Air Transport? By Edward P. Warner. 144. The Prevention of Fire in the Air. By Edward P. Warner. 145. Deflection of PropelIer Blades TThiIe Runn~C. By R. Katzmayr. Translated from Der ~~otor~agen, Aprfi 30,1922. 146. The Wing with a Pointed Tip. By Stephan -r. Prondzynski. Transited from Luftweg, March 23, 1922. 147. Effect of Periodic Changes of Angle of Attack on Behavior of Airfoils. By R. Katzmayr. / Translated from Zeitschrift fiir Flugtechnik und Motorlwftschiffakt, March 31 and April 13,1922. 14s. J3e~t,ReCta@ar and ~+haped ~ro~ sectiom for &rplane wing Spars. By R. Sonntag. Translated from Zeitschrift fiir Flugtecbnik und Motorluftschiffahrt, May 15, 1922. 149. Training of Aeronautical En=tieers. By Ed-p-rd P. Warner. 15Q. Air Tramport Economics. By Edward P. Warner. 151. Computati~e Examination of Bending Strength of Girclers Originally Cur-red and Sub- jected to Long Compressiori. By THlhehn Hoff. Translated from Zeit&hrift fiir I?lugtechnik und Motorluftschiffahrt,, April 13, 1922. 1~~. De-relopment of the Racing .tirpIane. By Edward P. Warner. 153. 31etal Construction of Ai.rcra.ft. By Edward P. Warner. 154. Principle of the Boerner Airship. By A. Kapteyn. TransIat ed from Premier Congres International de la Na-rigation Aerieme, November, 1921. ITO1.H. 155. The “ TItiversal” Adjustable and Re-mrsibIe PropeIIer Built by Paragon Engineers, Inc., Baltimore2 lld. 156. Method Rendering it. Possible, in Testing Airplane Wing 310cleIs at the Eiffel Laboratory, to Obtain Comparable PoIars Y7hether the Supports are Attzched to the Upper or Lower Side of ModeI. By G. EbBel. Translated from L’AerophileZ August 1-15, 1922. 157. Commercial Aviation in France. Translated from U.

No. 164. How to Lay out and Build an Airplane Landing Field: Notes on Shape and Size of Plot., Runway Details, Type and Arrangement of Buildings, Drainage of Field, Bes~ Kind of Grass, a~d Proper Marking to Aid Pilots. By Archibald Black. Taken from Engineering News-Record, Sept. 28, 1922. 165. Locatio~ of Center of Pressure of Airplane Wings. By Mises. Translated from Zeit- schrif t fur Angewandte Mathematik und Mcchanik, Feb., 1922. 166. Lessons of the Glider Meets. By Edwmd P. Warner. 167. Definition of Terms Used in Connection with Commercial Aircraft Engines. By Martino b Lagarde. Translated from Premier Congres International de la Navigation Aeriennet hTOV., 1921. \TO~. I~T. 168.Air Reactions to Objects Moving at Rates Above the Velocity of Sound With Application to the Air Propeller. By S. Albert Reed. 169. Effect of Method of Suspending Models in Airstream on Resulting Measurements. By C. Wieselsberger. Translated from Zeitschrif t fur Flugtechnik und l~otorl~lftschiflttl~rt, ~U].y 1~, 1922. 170, Et7ect of Temperature and Pressure on Watches Qnd (kronometers. By Mr. Leroy. Translated from Premier Congres International de la Navigation Aeriennc, Nov., 1921. Vo]. IV. 171. Causes of Failure of Airship Sheds. 1. Collapse of Airsh~p Shed A in Niedergorsdorf. By R. Sonntag. II. Suction Effects on Wind on Roof of Airship Shed “ Nerd” in St~aken. By W. Hoff. Translated from Zeitschrift fiir Flugtechnik und Motur- luftschiflahrt, Aug. 14,1922. 172.Balloon Fabrics made of Goldbeater’s Skins. By L. Chollet. Translated from I,’Aero- nautique, Aug., 1922. 173. Airplane Performance, Past and Preseni. By Edward P. Warner. 174. Commercial Airplanes and Seaplanes. Thick Wings or Thin Wings. AI] Metal or Mixed Construction. By Mr. Point. Translated from Premier Congres International de 1a Navigation Aerierme, Nov., 1921. Vol. IV. 175. Depreciation of Aircraft. By Edward P. Warner. 176. Influence of Design on Cost of Operating Airplanm. By Archibold Black. Taken from Mechanical Engineering, Dec. 1922. 177. List of Comercial .4ircraft Belonging to the Various French .4ir Navigation Comprmim as of August 31, 1922. Trans. from L’Auto, Nov. 19, 1922. 178. Airplane Speeds of the Future. By Edward P. Warner. 179. hTew Lateral Stabilizing Device for Airplanes, By Louis Constantine. Translahxl from Premier Congres International de la Navigation .Aerienne, Nov. 1921, Vol. IV. 1S0. Marcel Besso~ Wing Sections. By C. Delanghe. Translated from La Technique Aero- nautique, Oct. 15, 1922. 181. Soaring Flight and the Rh5n Contests. By Wllhelra Hoff. Translated from Zeitschrift des Vereines deutscher Ingenieure, ATOV.11, 1922. 182.Possible Improvements in Gasoline Engines. By S. Ziembinski. Translated from Prc- rnier Congres International de la Navigation Aerienne, Nov. 1921, Vol. IV. 1.s3. Soaring without Rising Currents. By Edward P. Warner. 184. Rules and Regulations of the 1922 Rhtin Soaring Flight Contest. Translated from Bc- richte und Abhand]ungen der Wissensehaftlichen Gesellschaft fur Luftfahrt, 1922, 185.Tlxecl Air-cooled Engines. By At H. Fcdden. Translated from Premier Congms Inter- national des de la Navigation Aerienne, Nov., 1921, vol. IV. 186.Lessons of the 1922 Rhon Soaring Flights. By L. Prandtl. Tnmslated from Zeitschrift fur Flugtechnik und Motcn-luftschiffahrt, Oct. 30, 1922. 1s7. Technical Section of Aeronautics. By Andr6 Lesage. Translated from Lc Genie CiviI, July 15, 1922. 1SS. The Laboratories of the Technical Section of Aeronautics. By Lt. Col. Robert.” Trans- . lated from L’Aeronautique, Dec. 15, 1922-Jan. 2, 1923. REPORT XM’IONAL ADVISORY COMMITTEE FOR AEKO&TAU21CS. 51

No. 1S9. Graetzin Special Carburetor. Translated from Flug-’iToehe, Dec. 7, 1921. 190. Longitudinal Balancing of Airpkmes. By .Uberh Eteve. Translated from Premier Congres International de Ia Navigation Aerienne, Nov. 1921,VOI. IV. 191. “.~” FletibIe Metal Joint. Trtinslated from the French. 192. “ AM” Gasoline Gock. Translated from the French. 193. Seaplanes for Commerce. By Ed-ward P. Warner. 194. Atmospheric Waves and Their Utilization in Soaring FIight. By 3L Albert Baldit. Translated from Comptw Rendus des Seances de l’Academie des S~ience, Jan. 3, 1923. .- 195. New Albatros Commercial Airplane “L 5S”. By G. Ueyer. Translated from Der Meter- wagen, Dec. 10, 1922. 196. Evolution of the Helicopter. By Karl BaIaban. Translated from Zeitschrift fiir Flug- technik und Jlotorluftschiffahrt, Nov. 15 and 30,1922. 19’7.Safety Factors in Aviation. By Louis Blerio~. Translated from L’.&erophiIe, Ott. I–15, 1922. 19S.The A’ew Interpretation of the Laws of Air Resistance. By L. Prandtl. Translated from the German. 1.99. My Experiments with Helicopters. By Etienne Oemichen. Translated from L’Air, Jim. 20,1923. 200.Aerial Photography-obtaining a True Perspective. Taken from London Times, .Ipril 5, 1923. 201.Wind-Driven Propellers (or “ Wind 31iNs”). By Max M. Munk. lkmslated from Zeit- sehrift fiir Flugtechnik und Motorluftschiffahrt, Aua-t 15,1920. 202.Wind Tunnel of Zeppelin Airship Company. By Max M. Mnuk. Tra.nslated from Zeit- scb.rift ffir Flugfiechnik und Motorluftschiffahrt, Jsn. 31, and Feb. 15, 1921. 203. Speed Limits of &rcraft. By E. EverLing. Translated from the German. 204. Hydrodynamic Tests for Determining the Take-Off Characteristics of Seaplanes. By R. Verduzio. Translated from Rendiconti deli’lkt.ituto Sp eriment aIe Aeronautic, No. 4, Dec. 15,1922. ?05,The A’e-iv French High-Speed Wind Tunnel By Lti. C!ol. Robert. Translated from L’A.eronautique, Jan. 1923. 206. Factors of %rfetty and Indexes of Static Tests. By Le Bailly. Translated from L’Aero- — plde, Dec. 1–15, 1922. 207. Rules and Regulations of the 1923 Rh5n Soaring Flighti Contest. Translated from Flugs- port, Feb. 21, 1923. ~OS. LTse of Helium in Airships. By G. .k%uro &occo- Translated from Reale Accadwnia 9aziona1e dei Lincei-Vol. 32, ~o. 2, Jan. 21, 1923. 209. Trend to be G1-ren A.erodynamical Research and Experiment. By M. Lepere. Trans- lated from LZAerophieIe, March 1-15, 1923. 210. Rules and Regulations Go~e.rning the Fokker Soaring-Flight Contest O-r-er Water or Level Land. Transited from Flugsporfi, “April 1S, 1923. 211.Replacing the Weight of Materials Consumed on Airships. By G. A. Crocco. Trans- lated from ReaIe Accademia Xazionale dei Lincei, Vol. 32, No. 3, Feb. 4, 1923. ~12. Wood Versus Metal in .bp]ane Construction. By H. Seehase. Translated from Zeit- schrift fiir F1ugtecbnik und Motorhrftschiffab.rt, k~os. 1 and 2, Jan. ’26, 1923. — ?13. “ Schmebeli” and ‘‘ Birger” Silencers. By Charles DoUfus. Translated from L’.Aero- nautiquel May, 1922. 214. The” Turkey Buzzard” GLider. By Roy G. Miller and B. T. Brown. Taken from Flight, .- April 12, 19,26,and May 3, 1923. 215. The Controls of an Airplane. By Edward P. Warner. 216. ~’ariable Pitch Propeller. By Enrico l%to~esi. Translated from L’AIa d’Italia, March- April, 1923. g17.controloperating31echanisms for .&h-planes. By Edward P. Warner. 52 REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS,

hro. 218.The “Autogiro.” By M. Moreuo-Caracciolo, Sec’y of the Royal Aero Club of Sptiin. Translated from Ingenieria y Construction, March, 1923. 219. Control Problems on Large Airplanes. By Edward P. Warner. 220. Bird ~]ight—~ints to be Obtained from it for Use in Aviation. By Dr. Magnan, SC. l). , Director of L’Ecole des Hautes Etudes, Paris. Translated from La Technique i4e~o- nautique, Dec. 15, 1921. 221. The Effect of Bow Stiffeners in Nonrigid Airships. By Edward P. Warner. ~2~, vor~icism in Aeronautics. By W. II. Sayers. Taken from The Aeroplane, Mar, 21, 28, Apr. 4, 11, 18, and 25, 1923. 223. on the Stability of OsciUations of an Airplane Wing. By A. C. Von Baurnhauer and C. Koning. Translated from the Ryks-Studiedienst Voor de Lucht~aart, Amsterdam. 224. Engines and Fuels. Translated from La Technique. Aeronautique, April 15, 1923. 225. Carburetion in Aviation Engines. By Naval Engineer Poincar6. of the S. T. Ae. Trans- lated from La Technique Aeronautique, April 15, 1923, 226. Absorbing Landing Shocks. By Edward P. Warner. ZZY. Lecture on Aerodynamics. By A. Toussaint. Translated from Ceritre d’Etudes de _ l’Aeronautique, TTersailles, Oct., 1922. ~~~. Gover~ent Relations \I,ith Air Traffic Companies and O\Vners of Touring ~~irp]anes. Translated from Bulletin de la ~hambre Syndicale des Industries Acronautiques. April, 1923. 229. Aviation Spirit—Past, Present and Future. By il. lZ. I)unstan and l?. B. ‘hole. 230. Control of Airplanes at Low Speeds. By R. McKinnon Wood.

BIBLIOGRAPHY OF AERONAUTICS. During the past year the committee issued a bibliography of aeronautics covering the yews 1917, 1918, and 1919 in one volume. It had previously issued the bibliography covering the years 1910 to 1916 in one volume. The bibliography for the years 1920 and 1921 in one volume wilI be ready for distribution in 1924. The bibliography for 1922 is in the hands of the printer, and should also be issued during the coming year. It is the policy of the committee to prepare and publish thereafter an annual bibliography. Citations of the publications of all nations are included in the language in which the publications originally appeared. The arrangement is in dictionary form, with author and subjcc ~ entry, and one alphabetical arrangement. Detail in the matter of subjeci reference has been omitted on account of cost of presentation, but an attempt lias been made to give sulllcien L cross-reference to make possible the finding of items in special lines of research.

FINANCIAL REPORT. The appropriation for the National Advisory Committee for Aeronautics for the fiscal year 1923, as carried in the sundry civil appropriation act approved February 13,1922,was $210,000, under which the committee reports expenditures and obligations during the year amounting to $209,591.53,itemized as foHows: Sdmies(induding en@neering staff) ...... $70,488.47 Wages...... -...... ----- 25, w. 2? Supplles andmateriaIs ...... 12,438. G1 Communication service ...... -...... 716.91 Travel ...... - ...... - . . . ..-= ...... 9,103. w Trs,neportation of things ...... ------~, 790.52 Furnieehing of electricity : ...... - ...... z_ ...... 1, 4G5.58 Repairs and alterations ...... 17,271.27 Eqtipmeut ...... 10,032.23 Structures and parta- ...... 14,480,96 Speci~l investigation ...... = ...... -35,700.00 Ptintlng and binding ...... 11,058.87 —.- Expenditwes ...... 209,991.53 Unexpended balance ...... 408.47 2:0,000.00 REPORT NATIONAL ADVISORY C031M1TTEE FOR AERONAUTICS. 53

In addition to the zbove, the committee had a separate appropriation of S15,600 for “Increase of compensation” to employees at the pate of $240 per annum. Under this appropriation the committee expended $15,460.10.

HELIUM A NATICEUL ASSET.

During the past year, for the first time, service airships have actualIy been inflated with heIium. The Na% rigid airship U. S. S- Shenandoah, and a number of Army nonrigid airships are now US=D helium. The improvement in the method of its extraction, referred to in the committee’s report of last, year, has materialized, and when further perfected wdl permit the production of helium at a much lower cost. Gases carrying helium in amounts adequate for quantity ~xtraction are found onIy in the United States. This exclusi~e possession constitutes a unique nationaI asset which shotdd not be dissipated. Even if any large-scale production of helium be not undertaken at this time, America should conserve this eskt~~ natural resource. The ~ational Advisory Committee for Aeronautics, therefore, strongIy recommends that Congress provide for the acquisition and seal- ing by“ the Goverrunent of the largest and best helium fiekk. RHATIOX BETWEEN #iERO~~VTI(2 RllSE.ARCHAND .UItCR.kl?TDESIGN.

OnMzy31, 1923, Dr. Joseph S. Ames, chairman of the executive committee of the Nationa] .idvisory Commiktee for Aeronautics, delivered the eIeventh annuaI Wilbur Wright 31emoriaI . Lecture before the Royal .4eronauticaI Society in London, the topic be@’ ‘Relation Between Aeronautic Research arid Aircraft Design.” The information presented in that lecture dealt entirely with the r~

ADVAIITAGES OF THE .AMERIC.KN SYSTEM FOR AEROA’ALJTiCAL RESEARCH.

The ~ationaI Advisory Com.miktee for Aeronautics is b-j- law specifically authorized to supervise and direct aeronautical research in the United States. England, France, and Japan have technical committees to either direct or advise in the conduct of scientific research in aeronautics. Our committee has naturally been always interested in the work of the foreign committees. For several years Lhere has been an exchange of technical information, partly by personal contact, buk principally through the mails. During the past year, however, three members of the National .Advisory Committee for Aeronautics, at different times, visited Europe, namely: Dr. Joseph S. Ames, chairman of the executive committee, who weni abroad to deliver the WiIbur Wright 3femoriaI Lecture before the RoyaI Aeronautical Society of Great Britain in May, 1923,and to gather information on which to base recommendations for next year’s research program in this country; Dr. S. W. Stratton, who went abroad primarily to partici- pate in the International Conference on Weights and Measures, but who took ad~antage of his 54 REPORT NATIONAL ADVISORY COM.MITTEE FOR AERONAUTICS. presence in Europe to investigate aeronautical progress; and Commander Jerome C. Uumaker, United States Navy, in charge of the design section of the Naval Bureau of Aeronautic, who went abroad on Nayy business, Each of these members on his return to America reported his observations and recommendations to the committee, and in this way the committee, in preparing its own research programs, has had the benefit of first-band information as to the progress and plans for aeronautical research in other countries. England has probably devoted more attention to aeronautical research, and in the past hus contributed more to the development of the science of aerona.uiic.s, than any o t.he.rcountry. AL the present time, however, America is probably making greater progress in aeronautical de~cl- opmen~, and is rapidly overcoming the advantage that England and France possessed fit the signing of the armistice. Doctor Ames, chairman of the executive comrnittw, in his report to the e~tire comrnittm, stated that English officials appeared to be much interested in how America had made such substantial progress as it was now making with younger and less experienced men conducting aeronautical researchj and with the expenditure of only a fraction of the sum spent on aerontiu- tical development in England. Doctor Ames stated that, in response to frank and direct questions from ofllcials of the British Air Ministry, he had stated thrit there were four rewons why America was making such progress i~ aeronautical research, namely: 1. That the members of the National Advisory Committee and of its standing subummlit- tees serve without compensation. 2. That our committee is an independent Government establishmerii, reporting directly lU the President, receiving its own appropriation from Congress, and, by virtue of such stwtusj is enabled to conduct any investigation it desires to unclert~ke, limited only by the funds avaihhlc. 3. That our resewch laboratories are located on a flying field where al~ phasrs of the work, including flight operations, are controlled and actuslly performed by the commitke’s own employees. 4, That there is splendid cooperation and coordination of effort in America, not only between the Army and the Navy themselves, but also betweeu both the Army and the Na,vy and the NTational Advisory Committee for Aeronautics, and that our committee cm and dots obtain from the Army and the Navy all aircrfift, equipment, and accessories needed in c.onncctiun with any in~estigation.

RELATION OF AERONAUTICAL RESEARCH TO NATIONAL DEFENSE.

Despite the progress that has been made in aeronautics, no one at this time cau safely predict its future or its limitations, either for purpose: of war or commerce. As to our natiomd defense, the programs of the Army and Navy are subject to Ghange from year to year and are dependent in large part upon the progress of aviation. And the progress iu a,viation is in turn dependent upon aeronautical research. The fact that the Imitation of armaments conference placed no limitation on the development of aeronautics for military purposes assures its greater relative importance in future warfare, whether over land or sea. Vi’ith the increase in expenditure in the maintenance of the military and naval air services, especially in view of the aggregate cost of new types of aircraf~j it is more than ever uecessary that fundamental information should be available on which proper design of new aircraf~ is based. The Army and Navy rely upon the Natiorial Advisory Committee for Aeronautics for the fundamental aerodynamic information requisite -for the design of military and naval aircraft. To keep pace with military developments abroad as welI as LOhflsten the day of practical commercial aviation in this country, more knowledge is necessary on the fundamental problems of flight. The committee from year to year has carefully prepared its research progrtims, but has invariably had to modify or delay their execution for lack of funds. The committee feels that the curtailment and postponement of its research programs mean the denial to the American people of knowledge necessary for the substantial development of aviation, civil and military, even though liberal appropriations be made, as they should be, for the Army, Navy, and Postal Air Services, REPORT NATIONAL ADVISORY COXMITT’EE FOR AERONAUTICS. 55-

The committee appreciates the need for econoruy in Government expenditures at, the present. time, but the continuous advancement of aeronautics places heavy demmds upon the committee for new knowIedge, ~hich cart be obtained only by the conduct of scientific research. The committee believes that the deveIopme~t of aeronautics WN promote our natiomd weIfare, increase our national prosperity} and make secure our national defense. T’Then considering the costs involved, it shnld be considered that scientific research is the best insurance obtainable to prevent waste of funds through the design and construction of aircraft which are not suitable for the purposes intended. The air services or our Army and hTavy are not so large as those of other world powers, but we are gradually forg~~ ahead of other nations in our knowledge of the scientific principles underlying the design and construction of aircraf$ and in this important respect at least we are providing a@nst unpreparedness in the air.

CONCLUSION’.

Dur&~ the past year there has been a gratifying increase in knowledge of the science of aeronautics, as fully described in the reports of the technicaI subcotittees ~d ~ the various publications of the NationaI Advisory Committee for Aeronautics. A year or more must usually elapse before the results of fundamental research become evident in the construction of better aircraft. Justtication of the poLicy of continuous prosecution of scientific research is reflected in American achievements of more popular interest during the past -year, among which may be mentioned the folIotig: (a) The five-day test demonstration by the Air Nail Service of the practicability of night flying of the mails, resutt~~ in the transportation of mails across the continent in both directions in from 27 to 30 hem-. (b) The completion of the first rigid airship t.o be built. in America, the N’avy tleet airship U.S. S. Shenandoah, formerly known as the ZR–I, -which has successfully passed the preliminary tests and which promises, under czreful handkg, to furnish reliab~e information as to the safety and practicability of airships in mwfare using hehm instead of hydrogen, and which may serve to open up a new era in air transportation and estabIish a new industry in America. (c) The winning by the American Navyj in international competition, of the Schneider cup for navaI seaplanes, when an American naval seaplane made a speed of 177 miIes per hour, which was 20 m.ik per hour faster than the newest competitor of any other nation, and 31 males per hour faster than the speed of the winning British seaplane-the year before. (d) The nonstop @ght by the Army Air Service across the conthent from coast to coast, or 2,520 miles, in 27 hours, in a T–2 airplane b which the Army had previoudy established the endurance record of 36 hours. (e) The estabhshment by the Navy in the Pulitzer trophy contest of a new official -worId’s- a.irplane speed record of 243.67 miks per hour over a four-Iap triangular course of 200 kilometers, an increase of 37.87 miles per hour over the winning speed of the year before; and the subse- quent. establishment of a record of 266.6 miles per hour over a straightaway course of 3 lrrometex. (~) The remarkable demonstration of poptiar interes~ in aeronautics on the occasion of the annual air races held in St. Louis, October 4 to 6> 1923, when, according to reliable reports, 150,000 people attended and 300,000 miles were flown in connection with the meet without casualit.y. These tiSible evidences of progress during one year compel recoamition of the fact that America, aIthough spend@g Iess money on aviation and maintaining smaller air services in the Army and Navy, is nevertheless abreast of other nations in the physical development of aircraf t. There has, however, been but little application of existing knowledge of aircraft, or air navigation, to commercial purposes. Broadly speaking, the situation with reference to the lack of commercial flying may be summarized as foIlows: (a) OnIy when reliable service at reasonable cost can be given miU American business men be ready for commercial aviation. Progress must be gradual. It musk rest upon a sound economic basis. Despite the remarkable physical development of aircraft, the present high 2:3—2+5 56 REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. cost factor, combined with the absence of improved national airways, constitutes an economic barrier to the general application of aviation to commercial purposes. (b) There has been no Federal legislation and but little State legislation to encourage the developmenfi of commercial aviation. The continuous prosecution of scientific research on the fundamental prohlcxns of flight IJy the hTational Advisory Committee for Aeronautics, tmcl the systematic collec~ion and dissemi- nation of technical information from all parts of the world, assure progress in tho dovelopmen t of fiircraft. Al~ho@ necessary, these activities alone are not suftieicnt LO assure t,ho carIy introduction of aviation into commercial pursuits generally. Costs must be reduced, but to accomplish this the development of commcrcial aviation should be given greater encouragement than it now receives from the Government. Tl~c present 10-year aircraft building program of the Ar_my Air Service und the 5-year program of tllo Navy will, if carried out, meet the absolute nee-ds of the Lwo services, and possibly serve to keep in existence a nucleus of an industry until a strong, se]f-suppor~ing comnuxwial aircraft industry develops. While there is seriQus question as to whether commercial aviation cm or should be pcrnm- nently maintained by the l’cderal Government, it is certain tha~ i~ can not get an earl,y start Wit]lout assistance+ The practical development of aviation in America WN no~ be realized until the Government gives intelligent support and eflective aid, principally by regu]rtting rmd lioensing and by cooperation with the States in the establishment of air-ways and landing fields. The Corn.mittee accordingly reaffirms its oft-repeated recommendation for the establishment of a Bureau of Civil Aeronautics in the Department of Commerce. The committee also strongIy recommends liberal appropriations for the dovelopmcn t of aviation in the Army and in the lNavy, At the present time the Army Air Servico is equipped largely with obsolete war-time airplanes and engines. These aircraf~ tare being rapi{lly exhausted, and at the present rate of appropriations the supply of equipment will become more inadequate each year. The Navy is also confronted with a serious shortage of aircraft. Bomb- ing exerciseshave taught the lesson that aircraft are absolutely necessary for mobile coast, defense, and that a navy without adequate aircraft will be EAa hopeless disadvantage in futuro warf tire. Major warships are being equipped with aircraft, but at the present rate of appropriations, fifter making due allowance for x ecessary replacements, the fleet will not be equipped with the proper proportion of aircraft. Whatever may be the dema~ds of economy, serious consideration must be given to the increasing relative import ante of aircraft in warfare and funds appropriateed to equip and maintain adequately the air services of the Army and Navy. Progress in aeronautics is being made at so rapid a rate that the only way to keep abreast of other nations is actually to beep abeud, year by year, never jidling behind. Respectfully submitted. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS, JOSEPH & AMES, Ckirmzzn Executive Committee.

8 APPENDIX TO ADNIINISTIWJ7WE REPORT

RELATIONBETWEEN AERONAUTIC RESEARCH Am AIRCRAFT DESIGN

s. AM-Es Chairman, Executire Committee National Advisory Committee for Aeronautics

APPENDIll TO ADMIMSTRATIVE REPORT.

RELATION IWIWEEN AERONAUTIC RESEARCH AND AIRCRAFT DESIGN.’

By IOSEFE % AXES, Chairman, Executive Committee, National Advimy Committee for Aeronautics.

INTRODLTCTION.

Ibis a greafi honor to be i..mritedto give the Wilbur Wright lecture on aeronautics, especially so for a fellow citizen of the Wright brothers. I think that I appreciate the honor dl the more because of personal relationships with Mr. Orville Wright and because, since the day of their flrstt successful cross-country ~~ht, I have had the opportunity of reaking the truly unique qualities of these great men. The fac~ can not be emphasized too often that, from the very — beg~~g of ~h& ~or~, ~he~ po~~ of T&=w ~as that. of the scientific instigator. Emptilcal methods, engineering development did no~ satisfy them; they wished to know the underl-tig scientific facts and to build on them. They had, in reaIity, the true concept of the purpose of the great aerodynamic ~~boratories of to-day. The selection of a subjectt for the TV.iibur Wright lecture is not an easy matter, especially when the seIection must be made months in advance and when, as in this case, the request was made to send the title by cable. I confess my title is comrnonplaee, but it was the best 1 could think of which wouId be sufiicientIy indefinite to alIo_ivme to include in the lecture the results For there is ~~ap a grave uncertainty in any of several imwastigations then in progress. — physical in~estigation as to the day when the results obtained will have sufficient value to be reported. . THE LANGLEY MEMORIAL AEROX~~TICAL LABOR.4TORY.

The aerodynamic Laboratory with which I am connected is the Langley Memorial Aero- nautical Laboratory, nob f m from Old Point Comfort, Vs., which has been de~eloped since 1915 by the Zational Advisory Committee for Aeronautics of the Uuited States. This committee ‘ is an independent Government agency, not under any of the departments, but reportingdirectIy to the President. We ha-re a laboratory for po=wer-plant inves~igations; a large wind tunnel of the type deve~oped by the N. P. L.; another tunnel in which the air may be compressed to 20 atmospheres or more; excelIent f ac.ilities for the desiagn and construction of instruments; and a large fleet of airpIanes, equipped for scientific purposes. In addition we are able to — engage the services of competent mathematical physicists fardiar -with akrodynamice. What . we ~ould IiIce to do would be to give free scope to these Iatterl and to conduct the laboratory tests under their direction, so that theory and knowledge of facts could make progress together. BUL this is not possible in an est abolishment whose primary purpose is to give advice to ‘other governmental services, especially adtice concerning questions raised by these sertices. It is true thak me can often inspire these questions, and ~e can aIways, in the process of obtaining the answers, Iearn more than is required. for the specific purpose. It follows, that whale we are conducting practicaI tests me are also doing fundamental scientific work continuoudy, exactly as a justice of a ~~h court expresses his deepest thoughts as obikr dicta.

~Thetlfrc~tkarmti ‘iViibur Wright memorial lecture, ddiwred in London before the Royal Aeromutical Rx&y of Great Britain, May 31, i9D, by Dr. Joseph S. Ames 59 60 REPORT NATIONAL ADVISORY COM.MIKCEE FOR AERONAUTICS.

THE DISTRIBUTION OF FORCES ON AIRPLAIVEPARTS.

As it hm hrrppined, two problems of a general nature have come to us this year from botL the Army and the Navy, which, while not new at all, have led t.o new methods rrnd to now knowledge. Both have an immediate bearing upon the design of aircraft; and it. ]VM for these reasons that I selected my rather indefinite tiile for this lecture. The first problem stated generally was to learn mqre about the distribution of forces on the parts of aircraft. It came to us in three cluestions: (a? How is the distribution of lorrd over a wing tip find ai~enm modified by chrrnging the plan form of the wing of an airplane? (b) Wily arc high-speed pursui~ airplanes subject to certain ~LYpCSof tic.cident, such m the ripping off of the linen envelope of the wings ? (c) What are the forces to which the fixed and movable surfaces an(l the envelope of fin fiir-

F[G,I.—The rebuilt Thonms Morse MB-3 airplane ready for wing and aileron pressure dis- ship are slul}jcxtt’d when it is tribution tests. makin~ manerr~ms ? The fis~ of these led to an extensive investi~aticm in the standar~l wind tunnel. One series of bests was on four model airfoils without ailerons, having square, elliptical, and positively and negatively raked tips; the second series was on wings having raked tips with ailerons adjusted to clifferent settings. The models had a chord of 6 inches and a mean semispan of 18 inches, and the method of images recommemied in one of the British R. and hl. reports was adopted in the investigation. A large number of series of openings were made in the surfaces of the airfoil and each was connected to a liquid manometer. The rc+ults give a grea~ defd of what is apparently new inf ormation concerning the air flow near the tip of a wing. They will soon be published both in tabular ancl in graphical form, so that designers can calculate with ease the distribution “of lift between the ends of the wing spars, the shears and bending moments, and the aileron efficiency. Further, with the knowledge obtained, proper distribution of load in sand testing is facilitated. The most important general conclusions are that tips with a positive rake give an erratic distribu-

● tion of lift near the tip of the aileron and that this may be a~oided by the use of a negative rake. Considerable new lighi is also thrown FLG.2,—EnIarged view of portion of wing skelcfon, showing tubes and surface comwtions for pressure distribution tests ou MB-3 upon the question of aileron balance. In order to study the air flow about a high-speed pumuit airplane, a Thomas ldol~e ifll- 3 a;rplane was rebuilt and suitably prepared for experimentation, Fig. 1. This has a maximum airspeed of 14.511. P. H. A large number of holes were made irr the two surfaces of both the upper : and lower wings; these were connected by rubber tubes (Fig. 2) to recording multiple manometers mounted in the f usel~ge; so in this way 60 records could be made simultaneously. The manometer, which has been described in published reports of the committee, consists of a series of metal capsules, across the middle of each of which is stretched a metal dirtphragm. In most of the tests the two holes facing each other on opposite sides of the ~~ing were connected to the opposite sides of the capsule; but in some cases only one hole was so connected, the other sido ●

RELATION BETWEE2T AEllONAUTfC RESEARCH AND AIRCRAFT DIISIGh7. 61

..- -.’

FIG. 3.—Wxlel in relief, slowing lift of MB-3 in steady fli~i zt 70 M. P. H. and 1,S3+3R. F. M.

Fm. 4.—Lift of wimg instea~g Eight at 711M. P. H. and l,W R. P. M. 62 REPORT NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. of the capsule being joined to a reservoir in the cocl@it communicating with a static tube whose opening was in the interior of the wing. Special attention was paid to the distribution of pressure in the slipstream and near the leading and traiIing edges. Since tLere is such a grea~ variation in pressure over a wing, each capsule was adjusted separately, so as to have the proper sensibility corresponding to the opening with which it was connected. At the leading cd,gc pressures as high as 200 lb./sq. ft. had to be measured, while farther back the pressure often did not exceed 30 lb./sq. ft. An accelerometer, a recording airspeed meter, n control position recorder, and an electric chronometer were also installed in the airplane. The information specially desired was the distribution of lift over the portions of wings in the slipstream during steady flight and that. over the entire wings during violent maneuvers. Measurements were made at air speeds of 70, I I 5, and 145 miles per hour, a@@cd, medium, and full throttle, under conditions of steady flight, and also during threc maneu vcrs, m roll, a flattening out, of a dive, and a vertical bank-at :50 ~~. P. 13. (,Figs~ 3, -1, 5, 6, and 7.) t !,.

.,. ,70 ($9 130 Im —.. _-— 90 m

~lG. 5.—Modelin relief, sbmving lift of MB-3 wings in a verticsl bank rd 1.%)M. P. EL and I,W R, P. M. Amgcration 4.2 g. Elc}-rtfor pulled up 12”.

The results can be understood most easily by the use of graphical nlethods. Contour lines of pressure may be drawn on a model of the wings; or, what is far more striking, three dimens- ional moclels may be constructed. Both these methods are illustrated. The numbers adjacent to any contour line indicate the total pressure upward in pounds per square foot, i. e., the com- bination of the effects on the two sides of the wing. The relief maps also give the combined eflects. Some of the most stril&g facts observed are: 1. The lift in the slipstream during steady flight is far from uniform on this airplane; at high airspeed and high engine speed a lift of 100 lb./sq. ft. was obser~ed on the leadin~ edge of the upper wing, while on the leading edge of the lower right ]ring there wm an area of dmvn pressure of 60 lb,/sq. ft. / 2. At low airspeed and high engine speed—that is, while climbing—there was at the trailing edge of the lower left wing, near the fuselage, a down pressure of 70 lb./sq. ft. 3. When the suction on the upper surface of a wing was measured with reference to the air inside the wing it was found to amount to as much SS 76 lb./sq. f~. in steady flight, whereas in one isolated point an inward pressure of as much as 24 lb.jsq. ft. was observed. RI?LATICJNTBETV=EX AER03-AUTIC:RESEARCH .A22D AIRCRAFT DESIGN.

FIG. 7.—ll0&din relief, pm~ective tiew, showiaglift of MB-3 W@S [D * Yti@ ~ ai I= M- P. H. snd t,~ R. p. ‘r. .4ccMeration 42 g. Elewdcx pulkd up 12”. 64 REPORT NATIONAL ADVISORY COMMITTEE rOR AERONAUTICS.

4. In flattening out of a dive the wings support only 80 per cent of the totaI load on the airplane, whereas in a vertically banked turn at 150 M. ??. H. where the acceleration rose to 4.2 g, the wings carried 90 per cent of the load, the remainder being borne by the fuselage and tail surf aces. 5. In steady flight a~ lLf5 M. P. I-I. the lift per square foot of the uppw wing is t}rice t,hat of ~he lower; the total lift of both wings being about 400 lb. greater than the vi’eighi of tl~e airplane, balancing the down load on the fuselage and tail. This fact is, no doubt, due to tllo rigging of this particular airplane; i. e., to the angular difference between the winas and to the Iower wing being almost at zero lift.

Ho. 8.—”C“ class airshipon which lhc pressure distribution work WaS done. .

‘=

FIG.10.—Controlsurfams of airship, showing Iacation of pressurepa~.. FIG. 9.—Prexure pad uwd onairah$ps.

It is important to add that this MB-3 airplane is a single-seater, so that the pilot has to control the airplane and press the button which starts alI the automatic recording devices. This investigation of the MB–3 proved so interesting and offered so many suggestions that further studies of pursuit airplanes have been called for, The plans are now perfected for simiIar inv-esti- gations of the latest types of military fighting airplanes, One problem in this connection is to compare the inherent advantages and disadvantages of monoplanes and biplanes. MEWURLYG THE PRESSURES OVER AIRSHIP SURFACES.

As is weIl known, the United St~tes is interested in the construction of airships. The hTavy has practically finishecl a large rigid, and the Army has well under way a semirigid. ~~isk- equally well known, the actual scientific knowledge of the aerodynamics of airships is not extensive. At the request first of the Navy ancl later of the Army, our Nat.ional Advisory Committee undertook to study and report upori the airship designs made by these two services. RELATION BETWEEN AERONAUTIC RESEARCH .%lTD AIRCRAFT DESIGN. 65

In connection with this work one of the technical staff of the committee, Doctor Murk, elaborated ~ certain theory of the airship which was distinctly noveI but led t-o results at variance with accepted practice- It was evident that red knowledge couId be obtained onIy by extemive experimentation on actua~ airships. Ti%at was needed primarily wzs & series of measurements of pressures over the envelope and surfaces of an airship when in steady ilight and when making

FIG. 11.–Fresiure Idistribution over bottom fin and rudder. I%ding fight.

maneu~ers. For this purpose a nonrigid airship, Nav type C (Fig. S], was placed at the disposal of the committee. It. is 200 feet. Iong, 40 feet in diameter, and has 200,000 cubic feet capacity. Pads were specialIy designed for the measurement of pressure (Fig. 9). Thwe lie practically flush with the enmdope of the airship, and each consists essentiall~ of a metal

FIG. 12.—Presure distribution .mrerbottom tin and rudder. Begirudng of eirdirrg tlight. —

box whose top and bottom surfaces are pear-shaped, roughly 2 inches by 4 inches, and he~d a distance of one orte-hundredth of an inch apart b-y means of studs; in the top pIate there are grouped in a comparatively smalI circle 22 holes, each three one-hundredths of an inch in diameter; z brass tube one-quarter of an inch in diameter series as an outlet from the box. Thk is connected by rubber or aluminum tubing to a liquid manometer in the car of the airship. 66 , REPORT NATION.4L ADVISORY COMMITTEE FOR AEROISAUTICS.

There are about 400 of these pads on t,he enve~ope and surfaces of the airship, 36 being in the bottom fin and rudder (Fig, 10). Simultaneous readings of 260 manometers may be made photographically. This investigation of the aerodynamics of an airship is noL yet comp~eted, but 1 can show you certzin observations which indicate the importance and novel character of the results being obtained. One illustration (Fig. 11) shows the pressure distributiori o-rer tb.e bottom fin rm~ rudder in circling flight; and the other when the airship, while in stendy flight, has its h ckn put hard down. The drawings do not require much explanation, but emphasis may be plticed up(m the results shown when circling flight is begun (Fig. 12). When the heIm is sud(lenly applie{l, ancl before the nirship attains an appreciable angular velocity, tb c angular acceleration creuf w surb a Errge force OD the vertical fins in the opposite dirwtkm to the force on the ruddrr that the net force on the stern of the airship is much smaller than has been supposed hitherto. It folh~ws that the condition of the sudden application of the rudder is no~ a serious one from the point (If view of the stresses in the hull of the airship. Presumably the reversal of the helm, when the airship is in a steady turn, does not cause a large increase of the bending moments beyond those already existing in that condition. These are the three problems referred to at the beginning of this pappr as requiring an elaboration of the methods for the study of pressure distribution; and no one crm question tho importance of the r.esulk obtained in the proper design of aircraft.

INVESTIGATION OF SCALE EFFECT.

Quite a diflerent set of questions has been asked our committee, which lead in {he pr~d to an in~estigation of the so-called scale effecL. Certain questions can, (of course, be alEwcrc(I on theretical grounds, and answerecl definitely; but. the great. majority can not. ,~ny ~ircraft is a complicated mechanism, macle up of many parts; all of these ha-w definite aero(ly - namicrd characteristics; but from a knowledge of these we can not pass to that of the mnchinc as a whole. The cIuestion as to the changes in forces and moments with scale, cspccirr]ly in maneuvers, is exceedingly difficult. The first in~-estimation which should be made on scale effect is to determine which aerodynamic proper~ies are most susceptible to the effect; after ~hat, the number of problems to be unclertdcn is practically infinite.

— -1

-,,’ . . L’ ‘, “, “1

.,, .,,., .. . ,”,,.,,...,,,. .,.!,...... ,: .:! .,.,, .“.. ,,. .,., ,, .,. El‘id“..ii- . .. . ., . . ,: .,, :.. i .. .,..:, . . A-Primarf rin honeycomb E-Secondur honeycomb H-Two -bladepropeier, (6’k2’-(52&5.O8cm fubes) (72’k2~-J“0.48x6.35cm tubes) 7 fooi(2.1S’4m) diameter B-Deffecfor F-Model l-Dead airspace C-.Liffbalance G-Weighf J-Balancer!hg D-Drag balance K-Door Fm. 13.—TheN. A. C. IL. variabte deusity No. 2 wind tunnel. RELATION BETWEEN .4ERONAt~TICRESEARCH .4XD AIRCRAFT DESIGX. 67

THE VARIABLE DENWTY JWND TUNNEL.

.AL Lm~lev. Field our committee has facilities for studfi~ scale. effect by four different methods, tw~ of which are: I believe, unique. We have an” or”tiary wind t~mel, having a 5-foot throat., and fitted with fans, so that an airspeed of 100 M. P. H. (147 feet per second) may be used: this gives a certain Reynolds number, not very large. A larger number may be obtained b.y a free fight method in which a large modeI is suspended below an airplane in steady flight; we have perfected methocls for suspension find measurement, and the results are, on the whole, satisfactory. To secure .a still larger Reynolds number, the committee has had constructed during the past year a wind tunnel to operate with air compressed to 20 atmospheres or more. The tunnel proper is 5 feet in dlzmeter at the experimental cbam- bek and is inclosed in a cylindrical tank with hemispherical ends (Fig. 13). The walls of the tunnel are hol]ow, providing an annular dead- air space in which the balance mechanism is inst ailed. This may be. cent rolled automatic- ally, or settings may be made by small electric motors, operated from outsicle, which attach or release heavy bahmcing weights hy means of cams, or shift k~hter weights aIorw FIG. 1+.–BJIMMrim forwind tunm~ No. Z. bahtnce arms. The model ~ attache~ to the b~lance (Fig. 14) by wires, there being three balance arms for measuring lift, drag, ancl pitching mo-rements. The ~ank is 35 feet lon~ and 15 feet in _ diameter and weighs S3 tons. It is mounted on a concrete foundation a~d is partially surrounded by a -working platform (Fig. 15). An observer on this makes settings and readings by looking into the tank throu@ small glass windows. The clensity of the air in the tank is controlled bF t~o compressors tilren l~j’ electric motors (Fig. 16). Continu- ous stages may be secured from one- tenth of an atmosphere to 20 atmospheres. Circulation of air is effected by a two-blade propelIer, of speeiaI design, 7 feet in diameter, and cIriven at 900 I?. P. M. by a 250-HP. s~n- chronousmotormounted on a separate found~t ion outside the tank. The drive shaft is made tight against air leakage where it passes through the head of the tank by a looseIy packed gland through which oil is circulated. The concept of such a tunnel was . -. originated by Dr. 31ax M. 31unk and this particular one ~as designed by him; and the mechanical equipment was designed and installed by IIr. D. L. Bacon, both members of the staff of FIG. 1.5.-YdabIe density wind tunrwI with obsemation pkstfmm and compreswr. the committee. The latter isin charge of the operation of this tunnel as well as of the other tunnels in the committees laboratory. It may be of interest to note that when the tunnel is operating at its greatest density it is equivalent m scale to a b-mnel 100 feet in diameter running at 60 miles per hour. It takes about an hour and a half to “ Mlate” the tank fully. 68 REPORT NATIONAL ADVISORY CO1fMiTTEE FOR AERONAUTICS.

Another method for obta.ini~g a large Reynolds number, which is used by the committee, involves the accurate measurements of ihe motion of an actual airplane in flight. To this end the staff of the committee have perfected a large number of recording instruments. Amol)g these may be mentioned a single-component accelerometer, a three-componen~ accclerompter, a three-col]]p(]I~e~lt, an

THE BOMB KYMOGIMPH. The latest instrument. cievclopr(l and one used in work about. wllicll I shall Spetllilater is a form of l;ymo- bwwph (Fig. ] 7), It eousists of a streamlinctl bwly, from tllo front, LIn(l of ~vhi(’h projects t~ NT.p. IA. pi~ot tube and }vhiclk has 1 tail appendage to render the whole (Iircctionally an(i longitudinally stable. There is a transverse shaft through the center FIG. 16.—Viewof wmiaMe densit y wind tunneI showing fan motor and air pipes.. of mass, to the two ends of which aro attzched suspension wires Ieading to winches in the cockpit of the airrdane, so thnt wlLeu [he [at ter is in fiigh t the kyrnograph may be lowered to a distance of :5 feet, so as to be in undisturbed air. In the upper fowarcl surf acc of the “bomb” there is w opening C1OSCAwith a cylindrical lens, outside of which is a small ~er~ical mirror, so that the rays of light from

Mirror /1;,., fi,.fer,cyindricailensond s/if / Shuffer .SIf Ekc iTiC}qht I!b[&’ .A ‘% . ./.~,,..../ ceriter of gravify m LMz!zJ- Arspeea’diophraqn

Fm. 17.—N. A. C. A, trailing kymograph-tdrspe~.d meter.

the sun may be reflected through the lens and then through two crossed slits onto a photographic film, The Pitot tube is connected to a capsule manometer, whose motions are recorded on the same film. This is wound on a.drum, inside of which is a constant spcml electric motor, driven by a current led in through the suspension wires of the instrument. An actual photograph of the records on the drum is given (Fig. 1S). FWLATION BETWEEN AERCJNAUTIC! RESEARCH AND &EiCR4FT DESIGN. 69

TVhen the airplane is ffown in a direction away from the sun the kymograph takes a position dong the direction of ihe relative wind, ~d a continuous record fl be made of the ang~ar poSition of the s~ ~~ r~w~ce to tfi fiection. An observer on the ground observes simuItaneoudy the altitude of the sun, and so one obtains a record of the a@e behreen the flight path with reference to the air and a horizontal line. The airspeed is measured at the

FIG.13-K.ymoTa@md. Airepeed records are fhe abarp cams. SIXIreecds are brmde~ti. szme time.j as is also the angIe of attack of the airplane itseIf. Therefore, if glicli~g-tlights me tnken, values of the rmtio of lift to drag may be measured at v-arious angles of attack at known zirspeeds. This method is obviously independent of ve+tical air currents. As an ilhiration of its accur~cy, a chart. is shown (Fig. 19) gi~~ the values of angle of glide with reference to airspeed v at different values of ~7, in which F is the airspeed, N is the number of revolutions per sec-

ond of the propeller, and D its diameter. By a preliminary model in~estigation it was found ‘hat‘he‘Ldue‘f h was 1.02 for the condition of zero torque. These and aU other “ free flight” tests under the directionof the committee have been carriedout by .W. l?.~. Norton and Mr. W. G. Brown with the aid of the committee’s most sldlful tesfi pilotl Mr. Thomas CarrolI.

~G. 19.—IIidicetedairspeedin?& P.1% CHidekt ofFokke.rD-VII.

With these fadities at the Langley Memorial .!mronautical Laboratory, it is hoped that rapid progr~s wiII be made in the ehwidat~on of the scaIe-&eci problem. Unfortunately for the purposes of this paper, the variable density tunnel was actually put into daily operation for observation purposes only about the first week in April, and so I can report the results of only two seriesof tests. l?orthisreason,although 1 have no cause to question their accuracy, they shouId, I think, be regarded as provisional. The first scale effect measurements undertaken were on spheres. There is nothing novel in this problem, but some of the resulk am interesting. Spheres of various sizes were studied in tke two tunnels, with their supporting spindles in the direction of tb e air stream and at various t-mglos to it (Fig. 20); other spheres were towed, suspended at &considerable distance below an airphwe,

.20

./6 F/qD2 ,/4

./2

./0

.08 0. 30 “ 60” 5u0 /20” /50° /80° /3 FIG. 20.—Effeet on resistance of sphere of direction of support with reference to air strcnm. Reynolds number is 2.5 x 1F. in flight; and finally certzin spheres were taken aloft by an airplane on pmticularly quiet days and allowed to drop, their motion being determined by theodolite observations from the ground. The results of all of these methods are given on the accompanying diagram (Fig. 2 1). This test was undertaken both to obtain large Reynolds numbers and to investigate the condition of turbulence in the new wind tunnel, If time were .a-railablej I would calI attention to sever~l interesting features of these curves.

[00 8U 60 .50 ,.

,40 . .._ ‘~. .,. ... : ‘, ---_...... _ --- - “- ,---.+ !.-,,, :, ~<..,,,.-.>% --,. ‘~. .30 ‘.. y.. ‘<:\ \ ‘ ,20 ,. \ \ ‘\ ‘“. i .“’,.:”” “’ - ‘“ ‘ “>:/”-!; “; \,,,,f ., L. . .. ‘ “~:L-;,....<.=’<.-.,:--‘“::;;;:...-----” j ! t. : ,,. , ,,. ,/0 ‘w, :, ‘. ,,, ,08 ‘\,,.,,,’::,5ti<’’”””+.“ .06 .05 .04 .03k , , . . ,,, ,, ,., - ,,, ,,... ) Reynoldskumbers x 10-S FIG. 21.—Curvw giving resistance of a sphere at different Reynolds numbers. RELATION BETRW.EN AEFWXAUTIC RESEARCH AXD AIRCRAFT DE51GX. 71

The second test on the subject of scale effect was made with reference to a type of airplane

using thick wings and ha.tig smaH parasite resisttince. ~ Fol&er D-Tql was selected for this purpose. .In airplane w-as equipped with suitable apparatus.; and a model of one-fifteenth scale

was made, which was fitted with its proper propeIler. Series of measurements on models and

.9 I ~’ 1 1’ I I

fk~e:ti~~e, + ! FE+{ f% 8FI , , / 7

Afmospher;cfu-ne/ 6

5 Q < 4

1 3 -! 1“ 1 2 1- J 1 I II 1 0 5 [o f520z?53335 ReynoMs number x /0-~ FIG. 22.-se ei%xt on K&dreg ratio using F&ker D-lx k-plane. PrOpeIler atzero torque. in full fl~ht have been made; the aerodynamic characteristics of lift and dr~o were measured at different attitudes, and the results obt ained are shown in the accompanying diagram (Fig. 22). If the use of these scale-effect methods justfies our present hopes, we shall be able in a comparati-reIy short time to place at the disposaI of the designer of aircmft a wealth of information which should increase markedly the accuracy of his work. -.,c),.—2~